cretaceous collembola (arthropoda, hexapoda) from the upper cretaceous of canada

Cretaceous Research (2002) 23, 165–188doi:10.1006/cres.2002.0313, available online at http://www.idealibrary.com on

Cretaceous Collembola (Arthropoda, Hexapoda)from the Upper Cretaceous of Canada

*K. Christiansen and †E. Pike

*Grinnell College, Grinnell IA 50112, USA; e-mail: [email protected]†972 Edgement Rd., Calgary, Alberta T3A-2J3, Canada; e-mail: [email protected]

Revised manuscript accepted 31 January 2002

Previously only one specimen of springtail (Collembola) has been described worldwide from the Cretaceous. The presentwork reports the results of an examination of seventy-eight collembolan specimens from Canadian Upper Cretaceous amber.Sixty-three specimens have been identified at the generic level, none of which belongs to extant genera. All are placed withineight newly erected genera. Most of these specimens belong to a single new genus, Protoisotoma, of the family Isotomidae.Also included are members of the broadly construed families Sminthuridae, Neanuridae, and Tomoceridae. Re-examinationof the type of Protentomobrya reaffirms its separate familial status. One additional specimen of an undescribed genus is placedin a new family. These data support a probable extinction of the Canadian arboreal Collembola fauna at the end of theCretaceous. � 2002 Elsevier Science Ltd. All rights reserved.

K W: Collembola; springtail; Cretaceous; Campanian; Canada; taxonomy; amber.

1. Introduction

The fossil history of the Collembola (springtails) is thegeochronologically most extensive of any hexapodorder, extending from the Lower Devonian (Hirst &Maulik, 1926) to the Pleistocene (Yosii, 1974).Unfortunately, there are remarkably few fossil recordsof Collembola over this long interval. There are onlytwo species reported from the Paleozoic. Rhyniellapraecursor was originally described from only fourspecimens from the Rhynie Chert of England (Hirst &Maulik, 1926), and has been redescribed several times(Tillyard, 1928; Scourfield, 1940; Massoud, 1967;Whalley & Jarzembowski, 1981), most recently byGreenslade & Whalley (1986) with the addition of afifth specimen. This taxon is remarkably modern instructure in spite of its age. Greenslade & Whalley(1986) placed the species in the modern family Isoto-midae. Doubts about the collembolan nature of thesefossils were expressed by Crowson (1985) and wereeffectively dealt with by Whalley & Jarzembowski(1981) and later by Greenslade (1988), who showedthat the doubts were the result of a misinterpretationof some structures seen in the fossils. Greenslade alsoindicated that possibly three species are represented.The only other Paleozoic Collembola is a single speci-men of Permobrya mirabilis (Riek, 1976) from theUpper Permian of South Africa. This fossil shows

0195–6671/02/$35.00/0

insufficient detail to allow a real comparison beyondthe family level.

The only Mesozoic specimens mentioned in reportsare from amber biocoenoses from the Cretaceous.Although Cretaceous Collembola have been reportedin literature (McAlpine & Martin, 1969; Zherichin &Sukatcheva, 1973; Pike, 1995), only one has beendescribed: Protentomobrya walkeri (Folsom, 1937)from Cedar Lake (Canada) amber. All recorded speci-mens are from Canadian amber (records fromTayjmir, Russia, were misidentified; V. Zherichin,pers. comm., 2000). Recently, specimens have beenrecovered from the Lower Cretaceous of Lebanon (D.Azar, pers. comm., 2001) and the mid-Cretaceousof Burma (D. Grimaldi, pers. comm., 2001). TheCanadian Cedar Lake amber is of uncertain LateCretaceous age but is probably Campanian(McAlpine & Martin, 1969). The single previouslyreported Cretaceous specimen was from this localitybut more recently Grassy Lake amber (75–80 Ma) hasyielded 78 specimens of Collembola. We have beenable to study the last mentioned specimens as well asa second specimen from Cedar Lake.

From the Cenozoic only four fossil deposits thatbear Collembola have been recorded: the middleEocene Baltic amber; lower Miocene amber fromChiapas in Mexico and the Sierra Septentrional of the

� 2002 Elsevier Science Ltd. All rights reserved.

166 K. Christiansen and E. Pike

Dominican Republic; and Pleistocene amber fromMizunami, Japan.

Material and methods

Most of the specimens we examined originated fromthe Royal Tyrrell Museum of Palaeontology (TMP)in Drumheller, Alberta, Canada; however, eightsamples, including the second collembolan specimenfrom Cedar Lake, originated from the CanadianAmber Collection of the Canadian National Collec-tion of Arthropods (CAS) in Ottawa, Ontario. Thetype of Protentomobrya walkeri Folsom originated fromthe Royal Ontario Museum (ROM) in Toronto. TheTMP specimens were discovered and prepared largelyby the junior author. The other seven specimens werealready prepared and in two cases the junior authordid further preparation.

All specimens were examined with two or threedifferent phase-contrast microscopes, a normal lightmicroscope, a phase-interference microscope, and aconfocal microscope. It is a remarkable feature of theamber materials that every specimen looks differentunder each microscope. Thus it was impossible toinclude in any one drawing all the features that wereobserved using all microscopy techniques. Our choiceof microscopes used for drawing was limited by thefact that only two microscopes had drawing arms.Drawings of features visible but unclear under thesemicroscopes were altered on the basis of whatwas visible under other microscopes. Features notvisible under these microscopes but seen with othermicroscopes were included in the descriptions. Thisdiscovery indicates that it is important in studyingCollembola in amber not to limit examination to asingle microscopic technique. All measurements are inmillimeters.

The labelling on the Royal Tyrrell Museum slides iscomplex and erratic. TMP indicates the Tyrrell col-lections, all of which come from the Grassy Lakedeposits. The first letters and numbers that follow areaccession numbers (i.e., 91.148.482). The firstnumber is the year of accession and 482 is the numberof the nodule from that collection. The numbers(sometimes present) following refer to the weightcategory of the nodule studied. Thus, TMP91.148.482, .7-1.7 indicates nodule 482 of sample148, which falls in a weight category between 0.7 and1.7 g. Sometimes a letter follows this and a number,which refers to the number of the sample studiedfound to contain an inclusion. Where a particularpreparation had more than one specimen of Collem-bola, the specimens were numbered on the label, andthese numbers are given in the locality record. We are

unable to decipher some of the meanings of the labels,and where this occurs they are simply reproduced.

2.1. Study area

The Grassy Lake amber deposit is located near thehamlet of Grassy Lake, Alberta, in tailings of anabandoned coal strip mine. The coal was depositedin situ (Pike, 1995) within the Foremost Formation ofthe Judith River Group (Eberth & Hamblin, 1993).The sediments within which the amber is found areolder than 72 Ma (Folinsbee et al., 1964) and prob-ably closer to 79 Ma (Eberth & Hamblin, 1993), thusprobably of Campanian age.

One specimen of a new genus from the CAScollections as well as the type of Protentomobrya origi-nate from Cedar Lake, Manitoba. Cedar Lake amberoccurs as a recycled secondary beach deposit ofHolocene age. This amber has been assigned a LateCretaceous age based on the existence of Grassy Lakeamber and the age of sediments that have beendowncut by the Saskatchewan River creating thebeach deposits, which range in age from Early Creta-ceous to Eocene. Amber has also been found insediments from 12 different locations of the samedrainage basin of this river. This further suggests thatthe Cedar Lake deposit must be a composite depositof ambers of different ages (Carpenter et al., 1937;McAlpine & Martin, 1969; Pike, 1993). Examinationof the Cedar Lake amber by infrared spectroscopyindicates that there are two distinct types of resinpresent in this deposit, but only one at Grassy Lake,additionally indicating the composite nature of CedarLake amber. This would indicate that the age of anyindividual nodule of amber from Cedar Lake is uncer-tain unless it contains a species contemporaneous withthose found at Grassy Lake. This was not true ofeither sample we studied. In spite of the evidence forits composite nature, some authors have consideredthat the deposit represents a single amber source(Borkent, 1995; Grimaldi & Cumming, 1999). Thislatter position is based on similarities in ceratopogonidflies found in both Grassy Lake and Cedar Lakeamber. However, we see no such similarity in thecollembolan fauna, although only two Cedar Lakespecimens were examined.

3. Results

Eight specimens were fragments identifiable only asCollembola. Seven specimens were identifiable onlyto the family or superfamily level. Sixty-three speci-mens could be identified generically, and all of thesecould be placed in one of eight undescribed, extinct

Late Cretaceous springtails from Canada 167

genera. Two, including Protentomobrya, could not beplaced in extant families or superfamilies. Of these 63specimens, 53 could be placed in a single new genus(Protoisotoma) of the family Isotomidae. Of the 25separate pieces of amber we examined containingCollembola, 11 pieces contained specimens ofProtoisotoma.

4. Systematic paleontology

Family: Protentomobryidae Folsom, 1937Genus Protentomobrya Folsom, 1937

Type species. Protentomobrya walkeri Folsom, 1937.

Remarks. Delamare & Massoud (1968) redescribedthis species, which originally was described by Folsom(1937), who placed the genus in a new family, Pro-tentomobryidae. While Delamare & Massoud thoughtit morphologically close to extant Isotomidae, theyconsidered that it showed an intermediate characterdeserving of separate family status. We concur withthis view. One character alone places it outside thepurview of all known Collembola. This character isthe dens, which is cylindrical and without differentia-tion into a dorsal or ventral surface. In addition, theapparent tapering of the dens is achieved largely by aseries of almost cylindrical subsegments, narrowing insize distally (see Figure 1A). As was noted by Dela-mare & Massoud (1968), the specimen is remarkablywell preserved. This condition makes visible two both-riotricha, attached in an unusual fashion on theventro-lateral surface of abdominal segment 4 (seeFigure 1B). Although the specimen is clearly uniquein these and a few other respects, the antennae arevery similar to those of Protentomobrya describedbelow.

The seven new genera of Collembola are describedbelow.

Family: Oncobryidae, fam. nov.

Diagnosis. Entomobryomorph Collembola withreduced first thoracic segment and abdominal seg-ments three and four similar in length; antennaefive-segmented, with the fourth segment very muchshorter than the third or fifth; eyes present; scales andlasiotrichia absent; dens tapered and flexible but with-out visible crenulation; mucro elongate with four largedorsal teeth.

Figure 1. Protentomobrya walkeri Folsom. A, end of left dens; B, end of abdomen showing bothriotricha (arrows).

Remarks. The large antennal segments fit Oncopodura,but no sensory setae are observed on the third andfourth segments. Clear large setae bases can be seen soit is possible they have been knocked off. The headand body have numerous, short, straight or curvedacuminate setae. The dens shows a division that isapproximately at the location of the division of thedens in Oncopodura, but only on one side, and thisappears to be an artifact of preservation. The dens isunlike that seen in either Oncopoduridae or Cyphode-ridae. The peculiar, small, fourth antennal segment isreminiscent of the third segment of Antennacyrtus(Salmon, 1941); however, there are no othersimilarities between these two genera.

This species cannot be placed in any extant family.The elongate, toothed mucro occurs within the Ento-mobryomorpha only in the Tomoceridae, Oncopo-duridae, Cyphoderidae, and the genus Troglobius ofthe Paronellidae. The tapered dens and absence ofscales or of socketed dental spines makes placement inOncopoduridae unjustified. The genus cannot beplaced in the Cyphoderidae due to the lack of scales,the presence of eyes, and the shorter length of thefourth abdominal segment when compared to that ofthe third. The Tomoceridae with elongate mucronesare found only in the Tomocerinae, and all taxaincluded in this subfamily have subsegmented and


long third antennal segments as well as scales andrigid dentes with spines. The genus Troglobius has anenlarged fourth abdominal segment and scales as wellas a straight dens. For these reasons we are creating anew family to encompass the unique combination ofstructures in this species. There is a single knowngenus, Oncobrya.

Genus Oncobrya gen. nov.

Type species. Oncobrya decepta sp. nov., Upper Creta-ceous, near Medicine Hat, Alberta, Canada.

Etymology. Oncobrya reflects the similarity to bothOncopoduridae and Entomobryidae.

Material. Type species only.

Oncobrya decepta sp. nov.Figures 2, 3

Etymology. Reflecting the deceiving superficialsimilarity to Oncobryidae.

Material. Holotype, CAS 1094, Grassy Lake, nearMedicine Hat, Alberta, Canada; collected byMcAlpine, Cooper, and Ware, June 1974. No ad-ditional specimens are known.

Diagnosis. The genus is quite unlike any known Col-lembola. The mucro and general appearance of thisgenus are like Oncopodura but there are many differ-ences. No scales are present, and while it is possible

they were lost, the good condition of the specimenmakes it highly improbable that they would be absentin the vicinity of the specimen. The mucro is verysimilar to Oncopodura but the basal tooth is at the baseof the mucro and projects upward rather than beingmore medial and projecting forward. The dentes aredifferent from the oncopodurid condition, beingtapered, curved, and lacking socketed spines or heavysetae. The mucro is very different from that seen inthe family Entomobryidae.

Figure 2. Oncobrya decepta sp. nov. Probable appearance in life (most setae omitted).

Description. Length, exclusive of appendages,c. 1.02 mm; five antennal segments with antennalsegments 1–5: 0.032, 0.072, 0.082, 0.018, and0.103 mm, respectively. The fifth antennal segment isswollen and the fourth is very small and constricted(Figures 2, 3B). No setae are visible on the last twosegments and the fifth lacks an apical organ. A fewacuminate setae are seen on the third segment andadditional setae occur on the second where theapex has a few long (c. 0.032 mm) types (Figure 3C);the rest of the segment exhibits shorter (0.012–0.022 mm), acuminate, smooth setae. Two possiblesensory setae are observed close to the apex and onelarge, probably ciliate, macrochaeta occurs nearthe base of the segment. Eyes at least two per side anda multilobed postantennal organ appears to bepresent. The vestiture of the head and rest of the bodyconsists of acuminate, smooth, mostly short (0.015–0.022 mm) straight or curved setae. Head and thoraxbearing a few larger curved setae (c. 0.040 mm) andsome abdominal segments with a median row of larger(0.050–0.055 mm) straight, possibly distally finely


ciliate setae. No scales appear on or near the speci-men. The sizes of the various body parts are: cephalicdiagonal, trunk, manubrium, dens, and mucro,respectively, 0.308, 0.814, 0.164, 0.205, and0.090 mm. One apparent unguis is visible in faceview; it is narrow with lateral teeth. Manubrium withonly one large (0.034 mm) dorsal acuminate straightseta. Dens curved, tapered, and bearing a few smallacuminate setae. Dens has a very short subapicalknob (Figure 3E). Mucro elongate (Figure 3D), with-out scales, but with a few slightly thickened setae(broken off). The mucro has one median tooth andno setae but the basal tooth is at the very base ofthe mucro and projects upward. Between the medianand basal tooth there are seven corrugations ordiminutive teeth on the dorsal surface. There are twoapical teeth.

Family: Tomoceridae s.l. Borner, 1913

Figure 3. Oncobrya decepta sp. nov., all figures of holotype. A, habitus. B, detail of antennae. C, enlargement of secondantennal segment, left side. D, enlargement of mucro. E, enlargement of apex of dens.

Remarks. This family is presently poorly defined. It ischaracterized by scales, when present, being coarselyribbed, having multilaterally ciliate setae and a fourthabdominal segment shorter or subequal to the third.There are two disparate groups of species. The first,sometimes called subfamily Tomocerinae, is currentlynative only to the Northern Hemisphere. The second,sometimes called subfamily Lepidophorellinae, is cur-rently found only in the Southern Hemisphere. Theformer always has scales and the third antennalsegment much longer than the fourth, and both seg-ments are clearly subsegmented. They have elongatemucrones and heavy dental spines. The latter hasshort mucrones, usually no annulations of the anten-nae, and the third antennal segment is slightly longer


or shorter than the fourth segment. The third abdomi-nal segment is much longer than the fourth. Dentalspines are absent or weakly developed. The new genusEntomocerus (below) clearly does not belong to theformer group, as it lacks antennal annulations, anelongate mucro, or clear dental spines, and has thefourth antennal segment similar in length to the third.In most of these features it is closer to the secondgroup. However, it differs in having the third abdomi-nal segment similar in length to the fourth and in theapparent absence of dental crenulations found in mostgenera of the subfamily. The mucro of Entomocerus isunlike that seen in any Tomoceridae but is nearestthat of Lasiofinus and Neophorella, although both ofthese genera have annulate antennae and lack scales.We originally considered placing the genus in a newfamily but decided that the Tomoceridae s.l. is suf-ficiently vaguely defined that it can be tentativelyconsidered a member of it.

Genus Entomocerus gen. nov.

Type species. Entomocerus mirus sp. nov., Upper Creta-ceous, CAS 4A, Cedar Lake, Saskatchewan, Canada.

Etymology. Refers to the similarity of the specimen tothe Tomoceridae and Entomobryidae.


Diagnosis. This genus is characterized by a lack ofsubsegmented antennal segments and a fourth seg-ment that is longer than the third. The second thor-acic segment has a dense collar of truncate to sharplypointed cylindrical mesochaetae. Some or most of themesochaetae on the mesothorax and those on the restof the body are multilaterally very finely ciliate formost of their lengths. The third and fourth abdominalsegments are subequal. The dens is slightly tapered,not dorsally crenulate, and without clear spines. Themucro is of moderate length, tapered but not pointed,and is covered with microsetae. The peculiar mucroand unsubsegmented antennae separate this genusfrom all other Tomoceridae.

Entomocerus mirus sp. nov.Figures 4, 5

Etymology. Latin, mirus, astonishing.

Material. Only the holotype, CAS 4A, Cedar Lake,collected by Martin and McAlpine, August 1965. Noother specimens are known.

Description. Length, exclusive of appendages,1.18 mm. Only one antenna seen, whose third and

fourth segments are strongly angled and distorted butlacking subsegments, and with the fourth segmentdefinitely longer than the third. Apical bulb present.Fourth segment has unusually densely packed, short(0.008–0.025 mm), stout, curved, acuminate setae;those nearer the base longer than those near the apex.Third segment badly distorted and compressed api-cally, with two basally expanded acuminate setae,c. 0.04 mm long. Remaining visible setae few, similarto those on fourth segment. Second segment clearwith setae 0.025–0.04 mm long, slender, smooth,acuminate, and straight to slightly curved; much lessdensely packed than on fourth segment. First segmentcompletely opaque but with at least a few cylindrical,apically pointed c. 0.05-mm-long mesochaetae. Headopaque, apparently lacking a vestiture of small setae.Anterior ventral margin of head with several long,slender, cylindrical, straight, and apically pointedsetae varying from 0.025 to 0.052 mm. Posteriordorsal margin of head with several 0.075–0.10-mm-long, forward-pointing, truncate, and finely multi-laterally ciliate macrochaetae.

The second thoracic segment has a dense anteriorcollar of mostly c. 0.10 mm-long cylindrical, truncate,or apically pointed macrochaetae. These macro-chaetae are finely and multilaterally ciliate. The bodyis mostly opaque and thus setae can be observed onlyin profile view. On the dorsum these setae are mostlystraight and 0.075–0.1 mm long. They are basallysmooth, but finely and multilaterally serrate for theapical two-thirds to three-quarters of their lengths.Two or three of these can be seen on each segment.On the fourth to the sixth segments there are alsocurved, slender, 0.15-mm-long, bothriotricha-likesetae. A similar 0.10-mm-long seta occurs on thesecond thoracic segment. The ventral portions ofthe abdomen have some less opaque areas where anumber of c. 0.10-mm-long, straight macrochaetaeare clearly seen to be multilaterally finely ciliate for theapical one-third to two-thirds of their length (Figure4B). The posterior portions of the venter displaycurved, 0.070–0.075-mm-long mesochaetae. Thelegs are clothed with 0.025–0.050-mm-long, mostlystraight, acuminate setae. Some on the femora appearto be finely ciliate.

Scales are numerous near the specimen and someappear to be attached to a piece of transparent,dislodged cuticle. Some scales observable on edgeprofiles are seen on the thorax, and a few possibleplan-view scales are seen on the clearer parts of theabdomen but are clouded by debris. The clearlyvisible scales are apically rounded and smooth orfinely lined, although some of the larger ones have oneor two ridges running their entire lengths (Figure 4C).


The manubrium is partly obscured by the opaqueabdomen, but the visible portion is without ventralsetae and has a few badly distorted large setae. Thedens is slightly tapered and curved but not crenulate.No ventral setae are visible, but dorsally there arenumerous (>20) moderately large setae. These aredistorted badly but most appear to be basally thick-ened and apically bent. Some shorter, straight setaeare also present, but none is clearly spine-like. Themucro is about one-fifth as long as the dens andwithout clear teeth. It tapers sharply and has micro-setae on its surface (Figure 4D). The dorsal edgeappears to be minutely serrate.

Family: Isotomidae Borner 1913Genus Protoisotoma gen. nov.

Type species. Protoisotoma micromucra sp. nov.,Upper Cretaceous, near Medicine Hat, Alberta,Canada.

Etymology. Greek, proto, referring to its probableprimitive evolutionary position in the familyIsotomidae.

Material. Type species and two probable additionalspecies.

Diagnosis. This genus is characterized by a greatlyswollen fourth antennal segment and a minute mucro,

0.005–0.0075 mm in length, which is less than 4% aslong as the dens. The dens is elongate and clearlycrenulate dorsally, with or without setae. The body isdensely covered with curved, acuminate, smooth setaeranging from 0.01–0.04 mm in length, plus erectpseudobothriotricha 0.045–0.078 mm long on theabdomen. The third abdominal segment is subequalto distinctly larger than the fourth. The postantennalorgan is simple and somewhat larger than the eyes.Eyes generally obscured by pigment, but at least fiveunits are evident on one side of a specimen. Unguesand unguiculus simple. The greatly swollen fourthantennal segment, in addition to the minute mucro,separate this genus from all genera of Isotomidae.

Protoisotoma micromucra sp. nov.Figures 6, 7

Etymology. Greek, micro, and mucro, referring to theminute mucro.

Material. Holotype, TMP, Grassy Lake, Alberta;91.148. 482 (2) 7–7.9 . 5, Slide 2, specimen 13;paratypes from the same locality, same sample, slide 1specimens 1, 2, 5, 6, slide 20 and slide ‘Fig. D’; TMP82.15.53 slide 1, specimens 2 and 3; TMP 91.148714. L 15.

Figure 4. Entomocerus mirus sp. nov. Probable appearance in life (most setae omitted).

Diagnosis. With characteristics of the genus and differ-ing from other species by the absence of dental setae.


Figure 5. Entomocerus mirus sp. nov., all figures of holotype. A, habitus. B, multilaterally ciliate setae. C, scales. D, dentes andmucrones.

Figure 6. Protoisotoma micromucra sp. nov. Probable appearance in life.

Description. Maximum length exclusive of appendagesis 0.54 mm. Body typically isotomid in shape (Figure6). Antennae four-segmented; the first segment verysmall. Fourth antennal segment 2.5–3.0 times as longas third and greatly swollen. This segment is clothedlargely with acuminate smooth setae on the main

portion ranging from 0.008 to 0.012 mm long, but theapices have a number (4 or 5) of short truncate setaewhich strongly project forward (Figure 7B). Thirdsegment generally shorter than second. No eyes seenon holotype but one paratype has at least five eyes anda probable simple postantennal organ. Five eyes seen


on one specimen (Figure 7E), and 1–3 on severalothers. Body densely clothed with short, slightlycurved, smooth, acuminate setae. At least one erectand slender pseudobothriotricha on each abdominalsegment (Figure 7D). Third abdominal segment onholotype distinctly larger than the fourth, but the tworange in size from subequal to the fourth slightly largeron paratypes. Foot with simple unguis (Figure 7C)and an internally sharply angled unguiculus. Manu-brium with setae; on the holotype and one paratypethere are clearly basal ‘glands’ such as seen on Se-tocerura, Semicerura, and Procerura. Dens 0.52–0.70 aslong as body, slender, without setae, and dorsallycrenulate for two-thirds to five-sixths of its length.Mucro 0.005–0.006 mm long and either falcate orvery weakly bidentate.

Figure 7. Protoisotoma micromucra sp. nov. A–D, holotype. A, habitus. B, detail of antenna. C, detail of leg. D, detail of fourthabdominal segment showing pseudobothriotricha. E, head and eyes, paratype 148.482 specimen 1.

Remarks. Protoisotoma micromucra is remarkable inpossessing an extremely minute mucro. In this respect

it resembles most closely the recently describedentomobryid genus Capbrya and some membersof the isotomid genus Folsomotoma. It differs from thelatter in the swollen fourth antennal segment andsimple mucro as well as the paucity of dental setaeand absence of dental spines. The antennae bear astriking resemblance to those of Protentomobrya,but there are few other similarities to that peculiargenus.

This genus makes up 82 percent of the specimenswe saw that were identifiable to genus, and 72 percentof the specimens, which were identifiable fragments orwhole. It is remarkable that, in spite of the hugenumber of specimens, there was no single specimenthat displayed clearly all the characteristics of thegenus and species well. It is quite possible that thereare two or more additional species; however, these arenot named since they are so similar it is possible thatthey constitute infraspecific variation or show features


which have been destroyed in the type species. Thetwo best-characterized possible species are numberedbelow.

Protoisotoma form 2Figure 8

Remarks. This form is distinguished from the othersby the presence of setae on the dentes (Figure 8B) anda lack of truncate, finely ciliate, body setae. Theprincipal setae on the fourth antennal segment areshorter than in P. micromucra (Figure 8E, F) rangingfrom 0.004 to 0.006 mm. The setae on the dens varyin number, but in the most intact specimens thereappear to be numerous small ventral setae and onelarge apical one, as well as a scattering of longer dorsalsetae.

All specimens are from Grassy Lake, Alberta; TMP91.148.482, (2) 7–7.9 . 5, slide 1, specimens 4, 9,

Grassy Lake, Alberta; TMP same locality, slide 2,specimens 11, 15, 16; TMP 91.148.769, 1-1.9-1-4,specimens 2, 4; TMP 90.147.31; 91.148.764, speci-mens 2, 3; TMP 91.148.481, 1.9-1-3 36, specimen 2.

Protoisotoma form 3Figure 9

Figure 8. Protoisotoma form 2. A, habitus, TMP 91.148.764. B, dentes, same specimen. C, dorsal setae of body, samespecimen. D, habitus, TMP 90.147.31. E–F, antennae, same specimen. G, manubrium, TMP 148.481, 1.9-1-3 36specimen 2.

Remarks. This form is distinguished from the othersby the presence of longer, truncate, and extremelyfinely serrate or ciliate setae (Figure 9B). Unfortu-nately none of these can be observed under oil-immersion microscopy. The antennal setae are shorterthan those seen in species 1. It appears to share setaeon the dens with species 2, although only threespecimens have been seen.

All specimens are from Grassy Lake, Alberta: TMP91.148.685, K.14; TMP 91.148.761, TMP 89.15,1-1.18, specimen 1.


Protoisotoma questionable species

Materials. Grassy Lake, Alberta, TMP 91.148. 789,1-1.9-19. This specimen fits P. micromucra well exceptfor the fourth abdominal segment, which is definitelylonger than the third 23–26, and the longest bodysetae, which are longer than those seen in mostspecimens of micromucra (0.078 vs. 0.045–0.07 mm inmicromucra). A simple untoothed unguis can be seen.The following would fit species 2 except for the longerantennal setae: TMP 91.148.533; TMP 91.148.481,7, 0.7–.79.4, specimen 4.

Specimens TMP 148.482 (1) specimens 1 and 2,and TMP 91.148.769 1-1.9-1-4 specimen 5 would fitspecies P. micromucra or species 2 except for anapparently relatively much shorter dens.

There are in addition the following specimens,which can be assigned to Protoisotoma but have insuf-ficient detail visible to place them further: TMP91.148.765, specimens 1, 2; TMP 91.148.769, 1-1.9,specimens 1, 3; TMP 91.148. 482, 7; 7-7.95, slide 1

specimens 3, 7, 8, 10; TMP 91.148. 482, 7; 7-7.95,slide 2, specimens 14, 17; TMP 82.15.53 specimens1, 4–7; TMP 91.148.765, 1-1.9, specimens 1, 2;TMP 91.148.164 G.S. 24, specimens 1, 4; TMP 82.15. 53 slide 2; CAS 1234, Grassy Lake, Alberta;collected by McAlpine, Cooper and Ware, June1974.

Family: Neanuridae s.l. Cassagnau, 1954Genus Pseudoxenylla gen. nov.

Type species. Pseudoxenylla fovealis sp. nov., UpperCretaceous, near Medicine Hat, Alberta, Canada.

Etymology. Reflecting its superficial resemblance togenus Xenylla.

Figure 9. Protoisotoma form 3. A, habitus. B, detail of thorax and head showing thickened setae.

Material. Holotype plus five additional specimensidentifiable to this genus plus one fragment probablyof the genus.


Diagnosis. This genus is characterized by 6+6 eyes,absence of a postantennal organ, unguiculus andfurcula, a rounded sixth abdominal segment withoutanal horns, lack of a molar plate and presence of largedeep foveae on the abdominal dorsum. The presenceof these deep foveae distinguishes this genus from allother Neanuridae with a rounded sixth abdominalsegment; eyes present and lacking a postantennalorgan.

Pseudoxenylla fovealis sp. nov.Figures 10, 11

Etymology. Latin, fovea, referring to the uniquestructural feature on the abdomen.

Material. Holotype, Grassy Lake, Alberta, Canada,TMP 91.148.296; I–1.19.26.

Description. Maximum length exclusive of appendagesis 0.758 mm. Body typically hypogastrurid in shape.Integument relatively uniformly granulate with granu-lations in pigmented areas 0.002–0.004 mm in maxi-mum length. Transparent areas, largely lateral parts ofintersegmental membranes, bear a clear, uniformlyhexagonal, pattern of sculpturing (Figure 11E), withmaximum diameter of hexagons about 0.003 mm.Antennae consist of the first two segments that areclearly separated but third and fourth segments fused(Figure 11B, C). A somewhat obscured apical organ,consisting of two guard setae and a fold, occurs at theappropriate position for the apex of the third segment.The holotype antennal segment lengths are: 1, 0.024;2, 0.032; 3+4, 0.072 mm. Few antennal setae are

visible but most are slender and smooth. One possiblythickened and external large seta is seen about one-third of the distance from apex to base of fused thirdand fourth segment. Cephalic diagonal, 0.16 mm.Eyes 6+6 (Figure 11D), one smaller and less clearthan the others. Lacking a postantennal organ.Mouthparts not clearly visible, but a mandibularmolar plate is clearly absent. Body segment lengths ofholotype in mm: thorax 1, 0.062; thorax 2, 0.091;thorax 3, c. 0.10; abdomen 1, c. 0.086; abdomen 2,0.090; abdomen 3, 0.062; abdomen 4, c. 0.094; ab-domen 5, c. 0.053, and abdomen 6, c. 0.025. Posteriormargin of sixth abdominal segment entire. Dorsum ofabdomen with clear foveae (Figure 11A): 2+2 onsegment 2; 1+1 on segments 3 and 4, and a weaklydemarcated second pair on segment 3. A possibleweakly demarcated fovea is seen on the anteriormargin of the left side of abdominal segment 5. Twosmall circular spots occur on the anterior margin ofthe dorsum of segment 6. Chaetotaxy of bodyextremely difficult to discern. The only setae seenwere at or near the lateral margin of the body. Theseare extremely slender, between 0.020 and 0.032 mmlong, cylindrical, and with very small setae bases,which make it uncertain as to where setae exist on therest of the body. Furcula, tenaculum, and unguiculuslacking. Ungues only seen in face-view, but apparentlypossessing both lateral and inner teeth. Two clavatetenent hairs seen on one foot of the holotype(Figure 7F).

Figure 10. Pseudoxenylla fovealis sp. nov. Probable appearance in life (most setae omitted).

Remarks. This remarkably modern-appearing speciesis superficially so similar to extant Xenylla in initiallyobservable features that at first we thought it should


Figure 11. Pseudoxenylla fovealis sp. nov. A–F, holotype. A, habitus with enlarged fovea. B, left antenna. C, outline of rightantenna. D, right eyepatch. E, reticulation of intersegmental area. F, hind unguis seen from inner edge. G, mid unguis,TMP 91.147.51 specimen 4. H, end of abdomen, TMP 91.147.51 specimen 1.

be congeneric; however, the well-developed foveae,fused antennal segments, a small sixth eye, and lack ofa molar plate led us to place it in a separate genus.Even though the head is pigmented, it is sufficientlytranslucent that it appears unlikely we would beunable to see a well-developed molar plate if such waspresent. The clear absence of a molar plate in theother putative specimens makes it very unlikely thatone exists. The two tenent hairs on the holotype areseen in face-view and apparently arise from the unguisas do two similar setae of five in another specimen. Inthe one specimen with a reasonably good lateral viewit appears that they actually arise from the tibiotarsusat the base of the unguis.

In addition to the holotype, we have seen fiveadditional specimens and one fragment attributable to

this genus. All have a similar body shape and lackfurcula, and for those where the foot is visible, lack anunguiculus. None has eyes clearly visible but twoappear to have minimally three eyes on one side. Noneshows any trace of a postantennal organ. Three ofthese specimens show 5–10 setae and have a pair oflarge, curved, cylindrical setae projecting backwardfrom the last abdominal segment (Figure 11H). Allspecimens where the segments of the body aremeasurable have the fourth abdominal segment longerthan the third, ranging from 1.25–1.6 times as long.None of the specimens shows all of the clear foveaeseen in the holotype, but several show 1–4 suchstructures. Two specimens have transparent areas inthe head and show no molar plates, although oneshows what might be a serrate mandible. The identity


of these specimens with the holotype remains in somedoubt, particularly because of variations in such fea-tures as the number of clavate tenent hairs, distri-bution of and number of foveae, and presence of large,heavy, posterior setae, all of which make it likely thatmore than one species is present.

Specimen TMP 90.147.50, C 5.25 is very doubt-fully a Pseudoxenylla. Only the posterior end is visible,which is only a mold of the body. It has numerouscircular and clear areas but these apparently areartifacts as they occur external to the specimen. Theimpression of an unguis is present but far from clear.The unguiculus appears to be absent and there arepossibly two clavate tenent hairs on one foot.

Of TMP 91.147.51, specimens 1, 2, 4, and 5,specimen 5 is observed from ventral view. The ventraltube can be seen but no setae are visible. The fusedthird and fourth antennal segments are clearly visible.No foveae are visible but adjacent specimen 4 has afovea visible on each of abdominal segments 1–3, andtwo clearly visible legs when seen under confocalmicroscopy, which appear to lack an unguiculus andhave 4–5 (Figure 7G) clavate, tenent hairs. Bothspecimens 4 and 5 appear to lack a furcula. Specimen1 has at least one evident fovea and several others thatare less clear. The head is translucent and while themouthparts are not entirely discernible, there clearly isno molar plate. Specimen 2 has a clear outline andtwo possible, very small anal horns. Possible butunclear foveae are present.

Specimen TMP 90.147.53, 83.15.3.30 Colb.Pod isa poor specimen but has two foveae on the fourthabdominal segment and two additional possiblefoveae on the third. There is no sign of a furcula andthe body has the same general outline as Bellingeria.

Family: Brachystomellidae Stach, 1949Genus Bellingeria gen. nov.

Type species. Bellingeria cornua sp. nov., Upper Creta-ceous, near Medicine Hat, Alberta, Canada.

Etymology. In honor of Peter Bellinger, whoseassistance in all fields of Collembola research wasinvaluable.

Material. Type species plus one questionableadditional specimen.

Diagnosis. This genus is characterized by a quadratemaxilla, absence of a mandible, and presence of awell-developed postantennal organ. The third andfourth abdominal segments are fused and the roundedsixth segment bears a small pair of dorsal anal horns.

The quadrate maxilla and lack of mandibles place thisgenus in the family Brachystomellidae. The fusedthird and fourth abdominal segments and analhorns separate this genus from all other genera ofBrachystomellidae.

Bellingeria cornua Christiansen & Pike, sp. nov.Figure 12

Etymology. Latin, cornu, horn, with reference to thesmall anal horns.

Material. Holotype, CAS 724, Grassy Lake, nearMedicine Hat, Alberta, Canada; collected byMcAlpine and Teskey, May 1973.

Description. Length exclusive of appendages is0.58 mm. Antennae clearly visible on only one side,four-segmented, but only extreme apex of first seg-ment is visible. Segments 2–3 about 0.03 mm longand segment 4 somewhat longer. Fourth segment withat least one distinct, moderately large, apical bulb andtwo or three short, curved, thick, blunt setae. Separ-ation between third and fourth segments is readilyvisible only at the region of the apical sense organ,which is delineated by a clear fold. The head is mostlytranslucent and no sign of a mandible could be seen.The maxilla is partly obscured but appears to be of atypical quadrate brachystomellid type (Figure 12C).Eyes at least five (Figure 12D), possibly six, per side.Postantennal organ composed of 6–8 large lobes andabout twice as large as largest eyes. Leg structuretypical of Neanuridae except that only one subcoxalsegment was seen (Figure 12E). Unguis unclear butapparently simple. No unguiculus was seen. Appar-ently long, single, truncate tenent hairs are present onthe two hind legs on one side. The ventral tube isevident but without distinguishable features. Theintegument is characterized by uniform granulesc. 0.002 mm in diameter. The third and fourthabdominal segments are fused and the sixth segmentis rounded. The furcula is unclear but appears to havea broad manubrium and reduced dentes with nomucrones; it is about three-quarters as long as thehind leg. The sixth abdominal segment bears a pair ofsmall anal horns (Figure 9F) on a small projectionfrom the end of the sixth abdominal segment. A fewsetae are present and all are small, curved, smooth,and acuminate.

Remarks. This unusual species has the general appear-ance of Brachystomellidae and the absence of mandi-bles as well as the apparently quadrate maxilla placeBellingeria in that family. The presence of anal spines


and fused third and fourth abdominal segmentsseparates this genus from all other genera of thefamily. A single specimen (TMP 91.147.51 specimen3), associated with specimens of Pseudoxenylla, may beincluded in it. It has a furcula very similar to, but moresharply defined than, that seen in the type of Pseudo-stomella. Unfortunately the specimen is so poorlypreserved that not much more than this, in addition tothe body outline, can be seen.

Family: Sminthuridae s.l. Lubbock, 1862Genus Brevimucronus gen. nov.

Type species. Brevimucronus anomalus sp. nov., UpperCretaceous, near Medicine Hat, Alberta, Canada.

Etymology. Latin, brevi, for the unique, short mucro.


Diagnosis. This genus is characterized by an extremelyshort mucro, from 0.11–0.13 times the length of thedens. It also features an extremely elongate maxillarystipes, reaching past the base of the antennae. Theantennae are not subsegmented and the fourth seg-ment is much longer than the third. The uniquely

short mucro separates this specimen from all othersminthurids.

Brevimucronus anomalus Christiansen & Pike, sp. nov.Figure 13

Etymology. Latin, anomalus, reflecting its unusualanatomy.

Material. Holotype, CAS 293, Grassy Lake, nearMedicine Hat, Alberta, Canada; collected by J. F.McAlpine, July 8, 1971.

Figure 12. Bellingeria cornua sp. nov., holotype. A, ventral habitus. B, dorsal habitus. C, maxilla. D, left side of head showingeyes and postantennal organ. E, hind leg. F, anal horns.

Description. Length exclusive of appendages is0.527 mm. Antennal segmental lengths in mm: 4,0.197–0.190; 3, 0.060–0.070; 2, 0.072; 1, 0.022.Fourth segment with a possible weakly-developedapical bulb (Figure 9B) and numerous curved, slen-der, and acuminate setae c. 0.02 mm long. A few setaeare longer (0.04 mm), and thicker setae are seen nearthe base of the fourth segment. Third segment withonly one visible seta, 0.022 mm long. Eyes unclear butat least eight seen on one side (Figure 9D). Mouth-parts with maxillary stipites extremely elongate androbust, extending to the posterior lateral portion of thehead capsule where they articulate with a thickening


of the capsular cuticle (Figure 13C). Maxillae unclearbut apparently small and pointed. Mandible absent.Head capsule without spines or outgrowths. Greaterabdomen greatly distorted and without visible detail.Hind tibiotarsal length c. 0.14 mm and hind femorallength c. 0.11 mm. Trochanter not seen clearly butapparently lacking any trochanteral organ. Foot com-plex not clearly seen but apparently with simpleunguis and unguiculus and bearing at least one mod-erately large, clavate tenent hair. Sixth abdominalsegment with 5+4 large, lateral, basally thickened,curved setae in dorsal and ventral pairs (Figure 13F).In addition, the median portion of this segment hastwo slender, acuminate setae and a median forkedseta. The manubrium is 0.076 and the dens 0.124 mmlong. Neither shows any setae. The mucro is veryshort (0.014 mm) (Figure 13E) and bears several,probably four, blunt lobes or teeth.

Remarks. This remarkable species has a mucro ofdifferent form and shorter length than that seen in anyother sminthurid species. It also displays a peculiarmaxillary stipites similar to those seen in Stenognath-riopes and Stenognathellus but appears to have little elsein common with either genus. The absence of a

mandible again is unique. The specimen exhibitsbasally enlarged setae on the sixth abdominal segmentand a median forked seta similar to those seen in someArrhopalites and some members of the Katianniformiaof Bretfeld (1999). However, the absence of a man-dible and the distribution of the enlarged sixthabdominal setae remove it from this grouping.

Genus Keratopygos gen. nov.

Type species. Keratopygos megalos sp. nov., UpperCretaceous, near Medicine Hat, Alberta, Canada.

Etymology. Greek, kerato, horn, and pygos, buttocks.

Material. Type species plus one specimen of aprobable second species.

Figure 13. Brevimucronus anomalus sp. nov., holotype. A, habitus. B, head showing antennal setae. C, enlarged articulationbetween head capsule and stipites of left side. D, enlarged detail of left eyepatch. E, dentes and mucrones. F, end ofabdomen, seen from above.

Diagnosis. Keratopygos is characterized by the pres-ence of a blunt, extremely large, dorsal projectionfrom the sixth abdominal segment. The fourth anten-nal segment is much longer than third and with a fewsubsegments. The legs bear several (six in the typespecimen), slender and clavate tenent hairs. Thereis a well-developed female subanal appendage; the


mucrones are long and smooth, and the dentes lackspines. The numerous slender clavate tenent hairs andpeculiar sixth abdominal projection separate thisgenus from all other sminthurids.

Keratopygos megalos sp. nov.Figures 14, 15

Etymology. Greek, megalos, large, referring to the largeanal projection.

Material. Holotype, CAS 110, Grassy Lake, nearMedicine Hat, Alberta, Canada; collected by Martinand McAlpine, 1968.

Description. Length exclusive of appendages is0.402 mm. Cephalic diagonal 0.13 mm. Antennallength in mm, approximately: 4, 0.060; 3, 0.035; 2,0.024; 1, 0.011. Fourth segment with five or sixsubsegments. Eyes present, but the head is opaqueand only two or three corneal profiles can be seen.Fifth and sixth abdominal segments sharply divided.Sixth segment with two large lobes (Figure 15A, E),between which there is a large (0.08 mm) micro-setaceous or striate dorsal projection (Figure 15C, F,I). A small, more ventral, median lobe bears a medianforked seta (Figure 15D); the large lobes bear large,curved setae and smooth, curved, acuminate, subanalappendages (Figure 15E). Hind tibiotarsus 0.130 mmlong; claw not clearly seen but apparently simple withsmall lanceolate unguiculus. Six slender, clavate ten-ent hairs per foot (Figure 15B). Ventral tube unclearbut without any visible tubercles. Manubrium 0.094,dens 0.13, and mucro 0.06 mm long. Mucro graduallytapered, without basal seta and with a smooth margin.No thickening at inner basal dens, as seen in extant

Collembola. No setae are visible on the manubrium ordens.

Remarks. A second specimen (Grassy Lake, Alberta:TMP 90.147.65, 80–17.1–80; Figure 16) almost cer-tainly belongs to this genus. The general shape,antennae, and furcula are all very similar. A structuresimilar to the dorsal appendage on Keratopygos can beseen directed ventrally; however, there are two largebubbles on the dorsum of this segment and it ispossible that these have pushed the structure into itsdownward position. Unfortunately, the distal ends ofthe tibiotarsi are not visible, so it cannot be deter-mined whether there are multiple, clavate, tenenthairs. At least six eyes are present in this specimen. Itsplacement in this genus must remain tentative.

The presence of six thin, clavate tenent hairs, asubanal appendage not directed towards the anus, thesmall number of antennal subsegments, and the obvi-ously divided fifth and sixth abdominal segmentswould argue for placement in the Katiannida (Bretfeld1986). However, the divided nature of the sixthabdominal segment and the dorsal projection is notseen in any member of this family. This latter struc-ture is slightly reminiscent of the projections on thegreater abdomen of some species of Papiroides. How-ever, these projections are on the mid-section of thesixth segment, whereas those in Papiroides are on thegreater abdomen. In addition, the antennae, the mul-tiple slender, clavate, tenent hairs, and the subanalappendages collectively place these specimens in adifferent group.

Miscellaneous specimens

Figure 14. Keratopygos megalos sp. nov. Probable appearance in life (most setae omitted).

Remarks. We studied a number of other specimensthat were too poor to be tentatively placed in any


Figure 15. Keratapygos megalos sp. nov., holotype; A–E from above. F–I from side. A, habitus. B, distal end of hindtibiotarsus. C, detail of sixth abdominal segment (arrow points to dorsal horn-like projection). D, setae of median lobeof sixth abdominal segment. E, left lateral lobe of sixth abdominal segment. F, habitus. G, antenna. H, hind unguis andunguiculus. I, horn-like projections of sixth abdominal segment.

genus. Some of these were totally unidentifiablefragments. However, eight are worthy of some note:

Tomoceridae Tomocerinae specimen TMP, GrassyLake, Alberta: 79.15.7.13, 96.9.213 (Figure 17). Thisspecimen shows the long, annulate, flexible thirdantennal segment (Figure 17A) characteristic of thesubfamily Tomocerinae. The fourth antennal segmenthas been lost and unfortunately the furcula also isabsent. This prevents comparison to the extant generaof this subfamily. The unguis cannot be clearly seenbut appears to be simple with small, internal, lateralteeth (Figure 17C, D). There are no lateral pseudony-chia, but under confocal microscopy one or twomedium, clavate tenent hairs are seen. The body isentirely covered with overlapping scales, which vary instructure. Some are extremely finely striate, others

moderately ridged and still others smooth, each bear-ing a central large ridge. The separation between theabdominal segments is very difficult to determine, butit appears that the first abdominal segment is consid-erably longer than the third. No clear demarcation canbe seen between the third and fourth abdominalsegments. There are numerous smooth macrochaetae,primarily in the mesothoracic collar, but also on thethorax and abdomen. A possible trochanteral organ,not clearly observable, appears to have about five orsix setae. Since this is the specimen having the mostmodern aspect, it is regrettable that the furcula isabsent.

TMP 91.148.767, 89 1.15–1.18, specimen 2 (Figure18A). Isotomid in appearance but the apparent fourthabdominal segment is twice as long as the third.


Figure 16. Keratapygos? sp.; all figures of specimen TMP 90 147.65. A, habitus. B, enlarged head. C, horn-like terminalabdominal projection. D, furcula.

Mucrones unclear, but dentes are only slightly longerthan manubrium. Lateral margins of abdominal seg-ments 3–5 with unusual angular projections. Underconfocal microscopy, some apparent eyes are barelyvisible.

TMP 82.15–53. Specimen one with similarly angledcorners on some abdominal segments but the thirdabdominal segment appears to be longer than thefourth. The furcula region cannot be seen because ofthe poor preservation of this specimen.

TMP 148.482 (2), specimen 12 (Figure 13C, D)Neanuridae s.l. Very young specimen, possibly firstinstar, with head about one-half the body length.Total length 0.23 mm. Body densely pigmentedbut dens and mucro extended posteriorly. Posteriormargin of the sixth abdominal segment apparentlybilobed. Internal features of body segments not vis-ible. Mucro about one-third as long as dens; mucronot clearly visible but apparently slightly curved andsimple, possibly with a very small internal tooth.Dentes simple. Only apex of manubrium visible butapparently deeply divided in the middle. Body seg-ments difficult to establish, but bases of the first andthird legs on the left side are visible. The threethoracic segments are about as long as the abdomen.

No other features of the legs are visible. The abdomi-nal segments are weakly demarcated, but all six appearto be present, albeit the sixth is very small, bilobedand projecting upward, apparently directly above thefifth segment. The head is translucent, and themandible lacks a molar plate and appears to have asingle apical, incisor tooth and two very small sub-apical teeth. A possible simple maxilla is seen some-what posterior to the mandible. The antennae aredirected such that detail is absent. A possibly lobedpostantennal organ can be seen in profile view on theleft side.

TMP 148.481, specimen 3 (Figure 18B). Neanuri-dae? All that can be seen is the silhouette. Theexternal outline is very similar to the neanurid speci-men seen in 148.482 (2), specimen 12, except that nofurcula is visible. The specimen is nearly opaque sothat mouthparts cannot be seen. The only differencebetween this and the specimen above is the existenceof some very thick setae on this specimen.

CAS 908, Grassy Lake, near Medicine Hat, Alberta;collected by McAlpine and Teskey, May 1973 (Figure18E). Not much more than an external profile isvisible on this specimen. It evidently is a hypogastru-rid and apparently has anal horns. No ungues or


furcula can be seen. Structures interpreted as possiblemacrochaetae are present.

CAS 141, Grassy Lake, near Medicine Hat Alberta;(26) collected by P. Boston, 1963 (Figure 18F, G).Clearly an isotomid but an early instar. Small (0.5 mmin length) and displaying a disproportionately largehead. The body has numerous large and small setae,but all are smooth and acuminate. Some of the setaeon the sides of the head and mesothorax are almostspinose. The mucro and dens are not visible. The fifthand sixth abdominal segments appear to be very short;the fourth antennal segment is disproportionatelylong. This specimen is similar to Protoisotoma, but thefourth antennal segment is not swollen. A vagueoutline of the legs can be seen but these are soobscured by the adjacent dark body mass as to affordno useful delineation of features.

TMP 148.481, 7–0.79.4 (7), Specimen 1 (Figure18H). Hypogastrurid with rounded projectingabdomen. It appears to be very immature.

Figure 17. Tomocerinae? genus. A, habitus. B, detail of antennal segments 1 and 2. C, D, ungues, seen from inner face.

5. Discussion

There has been considerable examination of the col-lembolan amber faunas of the mid-Eocene and

Miocene, and one small study of Pleistocene amber.Among these are key studies on mid-Eocene Balticamber (Stach, 1922; Handschin, 1926a–c; Lawrence,1985), lower Miocene Chiapas amber of Mexico(Christiansen, 1971), lower Miocene amber of theDominican Republic (Mari Mutt, 1983), and Pleisto-cene Mizunami amber of Japan (Yoshii, 1974). Inthese studies, all specimens were identifiable to extantgenera and the dominant family in these assemblageswas the Entomobryidae. The lack of extinct genera isunique to Collembola among hexapod groups (seeTable 1). In our study of Cretaceous Collembola wehave found that none of the 63 identifiable specimensbelongs to extant genera. This is not particularlynoteworthy, as of the 121 Cretaceous insect generalisted in Carpenter (1992), only seven are extant. Atthe family level, these Collembola are similar to anumber of groups previously reported (Jarzembowski,1989; Labandeira & Sepkoski, 1993) with only twoout of seven families known to occur in the UpperCretaceous not found in mid-Eocene strata. Morenoteworthy is that not a single specimen, out of over70 specimens identifiable to a family, belonged to thefamily Entomobryidae. The dominant family in thesamples we studied is the Isotomidae, representedprimarily by members of one genus, Protoisotoma. Of


Figure 18. Miscellaneous specimens. A, TMP 90 147.65, 80-17.1-80, specimen 2. B, TMP 148.481 specimen 3. C, D.148.482,(2) specimen 12. E, CAS 908, Grassy Lake near Medicine Hat, Alberta, Canada, collected by McAlpine andTeskey, May 1973. F, G, CAS 141, Grassy Lake near Medicine Hat Alberta, Canada (26), collected by P. Boston, 1963.H, TMP 148.481, 7-.79.4 (7) specimen 1.

interest is that modern genera most similar to thisgenus are presently limited to Australia, New Zealand,and sub-Antarctic regions. Thus, the make-up of thearboreal collembolan community of the CanadianCretaceous was significantly different from modernfaunas and those occurring during the mid-Eocene,Miocene, and Pleistocene.

There are three possible explanations for thesemajor differences between the Upper Cretaceous andstratigraphically younger faunas. The first is that thedifferences are due to the small sample size from theCretaceous and thus are more apparent than real.The second is that the Canadian region was biogeo-graphically atypical during the Late Cretaceous andwas represented by a peculiar arboreal collembolanfauna. The third is that environmental degradationbetween the end of the Cretaceous and the mid-Eocene extensively altered the arboreal collembolanfauna. Since the sole specimen we have from thePermian belongs to the Entomobryidae, it is clear

that this family had evolved before the end of theCretaceous.

The first alternative of the three listed above ishighly unlikely, as the 63 specimens identifiable togenus is a greater number than that found in moststudies of subsequent faunas, all of which exhibit agreat preponderance of Entomobryidae. The second,by contrast, has two pieces of supportive biogeo-graphic evidence. No Collembola have been found inamber of the Taimyr Peninsula or New Jersey amber.Since Collembola are scarce in amber collections (V.Zherichin, pers. comm., 2001 and D. Grimaldi, pers.comm., 2001), it is possible that this lack of Collem-bola is attributable to inadequate sampling or tapho-nomic bias. Because Collembola are small fossils,typically less than 1 mm long, and frequently badlydistorted, they may be present in fossil deposits butnot recognized. The senior author discovered fromfour days of examination of amber from the TyrrellMuseum that it is difficult even for a specialist to


Table 1. Extinct versus extant genera of insects; data from Carpenter (1992) except for Collembola (our data).

Ordermid Eocene to Oligocene

(extant)mid Eocene to Oligocene

(extinct)per centextinct

Cretaceous(extant)

Cretaceous(extinct)

per centextinct

Hymenoptera 74 53 42 0 21 100Diptera 217 96 31 4 16 80Lepidoptera 0 29 100 0 0 100Trichoptera 11 11 50 0 1 100Neuroptera 3 12 80 0 3 100Coleoptera 35 132 79 3 27 90Isoptera 6 9 60 0 2 100Ensifera 8 13 62 0 9 100Phasmatodea 0 2 100 0 2 100Mantodea 1 1 50 0 0 100Dermaptera 2 1 33 0 1 100Psocoptera 10 6 38 0 0 100Thysanoptera 10 20 66 0 0 100Homoptera 40 43 52 0 19 100Heteroptera 62 56 47 0 1 100Ephemeroptera 8 12 60 0 7 100Odonata 8 15 65 0 4 100Archaeognatha 3 1 25 0 0 100Collembola 15 0 0 0 8 100

recognize Collembola in amber. A second piece ofevidence, which may support a unique fauna in theUpper Cretaceous of Canada, is that four specimensof the Lower Cretaceous amber from Lebanon, whichthe senior author is presently studying, are not conge-neric with any specimen occurring in the Canadianamber. All are members of the family Sminthuridaeand very close to the extant genus Sminthurus.

The third possibility is that environmental eventsdestroyed the extant arboreal Collembola faunabetween the Campanian and the mid-Eocene. Ac-cordingly, in this model, a new fauna evolved fromforms living primarily in the soil or possibly otherhabitats, or alternatively in a region relatively un-scathed by the environmental degradation. Support-ing this hypothesis is the fact that, while the familyEntomobryidae existed during the Permian and wasdominant in all mid-Eocene, Miocene, and Pleis-tocene arboreal faunas, it is absent from Canadian andLebanese Cretaceous amber faunas. The most likelycandidate for such environmental transformationwould be the ecological upheaval and extinction at theCretaceous/Tertiary boundary. Dealing with the con-fusing, often contradictory, research, opinion, andcontroversy surrounding this event is far beyond thescope of this work; however, recent research on plant-insect associations (Labandeira et al., in press) sup-ports a major extirpation of insect herbivores at theboundary. An event such as the global wildfire pro-posed by Wolbach et al. (1988), possibly resulting

from an asteroidal impact, could certainly have beensuch an event. Whatever the cause, many authorities(Tschudy et al., 1984; Wolbach et al., 1988; Johnson,1992) apparently would have agreed with the state-ment that ‘‘. . . North American land plants weredevastated from Alberta to New Mexico at the K-Tboundary . . .’’ (Cowen, 2000, p. 293). The causeof this devastation could also have wreaked havoc onthe collembolan community that was available forentombment in amber. The fossil record of theCollembola is far too incomplete to make any soundjudgment, but some combination of (1) arboreal Col-lembola from the Canadian Cretaceous being biogeo-graphically exceptional, and/or (2) eradication by theterminal K/T event is probable.

The discoveries made during this study present in-teresting phylogenetic possibilities and pose somepresently unanswerable questions concerning struc-tural changes in evolving lineages. The observationthat close relatives of the dominant genus of a Creta-ceous Canadian collembolan fauna are now limited toAustralia, New Zealand, and sub-Antarctic regions,would suggest that Protoisotoma-like forms were wide-spread during the Cretaceous. This opens the possi-bility that small mucrones and long slender dentes areprimitive characters for the furcula of the Isotomidae.The sporadic nature of the collembolan fossil recordand absence of Southern Hemisphere fossils makesany confident assessment impossible. No otherCanadian Cretaceous genus bears a close resemblance


to any extant genus. Additionally, the unique dentes ofProtentomobrya, as well as its peculiar bothriotricha,make it appear to be unrelated to any extant form,necessitating re-examination of the issue of the originof the furcula. It appears highly unlikely that the pecu-liar structure of these dentes could have been an effec-tive jumping organ, albeit what other function theycould have served is unclear. The short mucrones ofBrevimucronus and absence of mandibles are very dif-ferent from those of all extant sminthurid. Both Proten-tomobrya and Brevimucronus appear to belong to extinctlineages. The genus Oncobrya bears some resemblanceto the modern Oncopoduridae, but if it resembles anyancestral form, that would indicate that this familylost an antennal segment and developed scales inde-pendent of other scaled entomobryiform families.

Keratopygos displays many of the features of theKatiannida, indicating that this group existed in theCretaceous; however, its peculiar anal horn indicatesthat it belonged to a now extinct branch of that group.Bellingeria and Pseudoxenylla also exhibit peculiarfeatures suggestive of now-extinct branches of theirfamilies.

In any case, the Canadian Cretaceous fauna we havestudied is different from any known Cenozoic or mod-ern collembolan fauna. The number of taxa found,between 17 and 19, is similar to the number found inthe Chiapas and Dominican Miocene ambers, but ithas eight genera, of which none is extant. This isin marked contrast to the mid-Eocene and lowerMiocene amber faunas which together contain no ex-tinct genera and have yielded specimens of 23 extantgenera. This puzzling discrepancy between collembo-lans and other hexapods presents a challenge to paleo-biologists. It is likely that living representatives of fossilCollembola exist currently and have been overlookedin modern studies. Very close examination of carbon-aceous shales such as that done by Riek (1976) couldyield additional fossil specimens of Collembola. Inaddition, large amber collections such as the Alaskanamber at the University of California Museum ofPaleontology at Berkeley, and mid-Cretaceous de-posits in Burma at the American Museum of NaturalHistory (D. Grimaldi, pers. comm., 2001) have yet tobe studied. Such new evidence could determinewhether the phenomenon uncovered herein was globalor local, and thus may resolve the causes of the re-markable discrepancy between the Upper Cretaceousand subsequent Collembola faunas.

particularly thanks Jackie Wilke, Paul Johnson, andVien Lam of the museum for their assistance while hewas working there. He also thanks Robert Skidmorefor starting him on this project and for the loan of thespecimens from the Canadian Amber Collection, andJanet Waddington of the Royal Ontario Museum formaking possible the loan of the type of Protentomobrya.Summer Ventis prepared the drawings. We are grate-ful to Dr Conrad Labandeira for his many helpfulcorrections and suggestions. This work was madepossible by grants from Grinnell College. Dr PeterBellinger made many useful suggestions during thepreparation of this paper. Vicki J. Wade and StephaniePeterson and Summer Ventis were most helpful inpreparing the manuscript.

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