Pearce-Sellards Series 48 PROLAPSUS A LARGE SCIURAVID, RODENT AND NEW EOMYIDS FROM THE LATE EOCENE OF TRANS-PECOS TEXAS JohnAndrew Wilson and Anthony C.Runkel September 5,1991 TEXASMEMORIALMUSEUM,THE UNIVERSITYOFTEXASATAUSTIN CONTENTS Text Illustrations 1 15 Tables 19 References 28 John Andrew Wilson Vertebrate Paleontology Laboratory Texas Memorial Museum The University ofTexas at Austin 10100 Burnet Road Austin, Texas 78758 Anthony C. Runkel 2300 Howard Street, NE Minneapolis, Minnesota 55418 ThePearce-SellardsSeriesisanoccasional, miscellaneousseriesofbriefreportsofMuseumandMuseumassociated fieldinvestigationsand otherresearch. All manuscriptsare subjected toextramural peerreview beforebeingaccepted. TheseriestitlecommemoratesthefirsttwodirectorsoftheTexasMemorialMuseum:Dr. J.E.Pearce,Professorof Anthropology,TheUniversityofTexasatAustin,andDr.E. H.Sellards,ProfesssorofGeology,TheUniversityof Texas at Austin. Both professors are now deceased. ©1991 by Texas Memorial Museum The University ofTexas atAustin All Rights Reserved Printed in the United States ofAmerica This is publication No.-N.S. 35 of the Texas Memorial Museum Not printed with state funds 1 1991 Prolapsus: Sciuravidae ABSTRACT The questionably hystricognathous and hystricomorphous rodent Prolapsus is assigned, onthebasisofitsdentalcharacters,totheFamily Sciuravidae. Thecompletedentitionof Prolapsus sibilatoris is now known but P. junction!s is still represented by isolated teeth only.Prolapsussp.ofWood(1973)isnowidentifiedasaspeciesofPauromys. Prolapsusis found in the early Uintan (Uinta B) Whistler Squat local fauna and late Uintan (UintaC)Serendipitylocalfaunaatseveral localities inTrans-PecosTexasandisclosely related to a new eomyid genus, Aguafriamys, here described, that occurs in sediments of Duchesnean age in the same area. IfProlapsus is interpretedas being truly hystricognathousit follows that this character has evolved more than once. A new species of Yoderimys is described from theCoffee Cup local faunaof Chadronian age. INTRODUCTION Wood(1972, 1973)reportedthediscoveryof,anddescribedindetail,theEocenerodent Prolapsusfrom sediments then assigned to the Pruett Formation but now included in the , Devil’s Graveyard Formation (Stevens et al., 1984) of Brewster County, Texas. Wood (1973)recognized thatthe teethofProlapsusstronglyresembled thoseofmembersofthe Family Sciuravidae but did not assign Prolapsus to that family because of the fullyhystricognathous character of the mandible. Later, without including Prolapsus in a family. Wood (1975, p. 78-79) included the genus in the new infraorder FranimorphaalongwithotherNorthAmericanhystricognathsandlater(Wood 1977, 1981)statedthat a newly discovered skull (TMM 41672-11) was hystricomorphous. Since 1973, the Prolapsus sample has more than doubled and now includes two partialskulls, several more lower jaws (figs. 1-3) and many isolated teeth. One of the partialskulls, TMM 41672-11 is being studied by Dr. A. E. Wood and is the one referred to byKorth (1984:7). This paper will only refer to TMM 41672-11 for purposes of discussing thedentitionsoas notto interferewithWood’sstudyofthemorphologyoftheskull. We will mention, however, that the infraorbital foramen on the right side of the skull fragment ofTMM 41672-11 (fig. 2A) is incomplete on the dorsal margin, but as prepared, and judging from the ventral and lateral edges of the foramen, its diameter was about the size of M l . Following the suggestion of Ferrusquia-Villafranca (1989) this would be considered a small infraorbital foramen. However, the process of the maxillary that formstheexternal marginoftheinfraorbitalforamenisverythin andsimilartothatfound in the chinchilla. It is much larger than the infraorbital foramen in the cylindrodontsPseudocylindrodon texanus and Ardynomys occidentalis from the early Chadronian of the Vieja area. The Prolapsus material that was available to Wood (1973) was collected from the basal Tertiary conglomerate marker bed (localities TMM 41444 and 41443) and the Whistler Squat quarry (41372). Their stratigraphic positions in the Devil’s Graveyard Formation are shown in Stevens et al. (1984:figs. 5, 6). The faunas from these three localities were combined by Wilson (1984) to form the Whistler Squat local fauna and are associated withatuffthathasyieldedadateof46.9± 1.0Ma(Henryetal.,1986:23).TwoProlapsus Pearce-Sellards Series No. 48 teeth (42953-6, P. sihilatoris and 42953-7, P. junctionis) collected from the basal BigYellow Sandstone Member, Canoe Formation, in the Tornillo Flat area of Big Bend National Park are associated with a fauna that correlates most closely with the Whistler Squat local fauna (Runkel, 1988). In addition, Runkel (1988) reported on a locality on thenortheastflankofDogieMountainfromwhichanumberofProlapsusteethwere recovered. Thislocalityisdirectlybeneathanashdatedat46.29±0.04MabytheA40/39method attheUniversity ofCalifornia GeochronologyCenter. Isolated Prolapsus teeth from the Serendipity locality (41745) and isolated teeth and skull and jaw fragments from the Purple Bench locality (41672) are additions made subsequenttoWood’s 1973paper. TheselocalitiesarecombinedtoformtheSerendipitylocal fauna and lie between rocks dated at 43.9 ± 0.7 and 42.7 ± 1.6 Ma (Wilson, J. A., 1986:360). The Serendipity local fauna was assigned an age oflate Uintan (Uinta C) byWilson (1986). Thenewmaterialallowsustoreidentify twoupperP4s,41372-278and-297,assignedbyWood to Prolapsus sihilatoris (1973:figs. 7A, B) as belonging to a new undescribed genus and species and not to Prolapsus. Also newly known since that paper is the M 3 of Prolapsus junctionis. Furthermore, a large number of isolated teeth of Wood’s (1973) Prolapsus sp., the very small form, have been restudied by Walton (1986) and are now identified as Pauromys. Two new lower jaw fragments are of eomyids, one of which seems to be related to Prolapsus. - AbbreviationsAllspecimensofProlapsusarecurrentlyfoundinthecollectionsofthe Texas Memorial Museum (TMM). Specimen numbers without prefixes belong toTMM; such numbers preceded by a hyphen are abbreviated, and include the five digit localitynumberpreceding,e.g.,41372-1,-2. Detaileddescriptionsoflocalitiesareonfileatthe Vertebrate Paleontology Laboratory, Balcones Research Center, 10100 Burnet Rd., Austin, Texas 78758-4497. CM Carnegie Museum, Pittsburgh FMNH Field Museum ofNatural History, Chicago SDSM SouthDakotaSchoolofMinesandTechnology 1991 Prolapsus: Sciuravidae 3 Family Sciuravidae Miller and Gidley, 1918 Prolapsus Wood, 1973 - Genotype Prolapsus sibilatoris Wood, 1973 - Referred species P. junctionsWood, 1973 - , Emended Diagnosis [modified from Wood (1973)] Dental formula I */,, C °/0P 2/j, M V 3. Questionably hystricognathous with angle arising entirely laterad of incisive alveolus; lower premolar smaller than molars; lower cheek teeth with transversely elongatemesoconid that may be single, double, or lophate; molar metalophid extending from protoconidto rear surfaceofmetaconid,closing rearoftrigonidbasin;anteriorcingulumwith very small anteroconid or without anteroconid, usually a forward opening of trigonid basin at one or both ends of anterior cingulum; lower teeth with partial or complete crests from entoconid toward hypoconid, with a cusp-like enlargement in the center of the crest on some teeth; posterolophid reaching to or nearly to entoconid, hypoconulids present or absent; P3 is a simple peg, P4 with or without a hypocone; M 1 andM 2 quadrate, M 3 subtriangular; M 1 and M 2 with large and distinct hypocone, M 3 with hypocone close to protocone; protoloph usually complete after moderate wear; anterior cingulum large with or without protostyle; anterior arm of hypocone on M 1 and M 2 widely separate from protocone and protoloph and continuous into central basin, almost to paracone, forming a pseudomesoloph; single or multiple metaconules connecting with hypocone in varying manners; strong posterior cingulum; prominent mesostyle or mesostyles;lowercheekteethwithtworoots,oneanteriorand oneposterior;uppercheek teeth with one lingual and two buccal roots; upper and lower incisors with flat anterior face, enamel extending well onto lateral side; incisor enamel uncertain*. - Distribution. Uinta B and C, middle Eocene, Devil’s Graveyard and Canoe Formations, Big Bendregion ofTexas. Prolapsus sibilatois Wood, 1973 Figures 1-5, Tables 1-4. - Type. TMM41372-179,rightlowerjawwithM,.3,thealveolusofP4, abrokenincisor, and a broken angular process. - Material. 41372-778(Wood’s-241C),I,;-299,LP4; -284,LM,;-291,RM,;-266,RM 2; -143,LM,;-265.RM,;-269,RM,;-381,RM,;41672-8,LP4-M,;-9,RM,-M2 ;-14,RM,;-15, LM,;-85RM,,M,;-86.RM,;-106,leftlowerjawfragmentwith P4-M,;-198,leftlowerjawfragmentwithP4-M,;41745-84,LP4; -58,RM,orM,;-89,LM,orM,;-142,LM,orM,; -272,RM,;-278,LM,orM,;-307,LM,orM 2;-308,LM,orM,;-309,LM,orM,;-310,LM, orM,;-311.RM,orM,;-314,RM,orM,;-315,LM,orM 2;-317,LM,orM 2;-318,LM,or M,;-319,RM,orM 2;-316,RM,;-371,RM,;-377,RM,;-378,LM,;-379,LM,;-380,RM,; * Wood (1973. p. 22, 27) identified the incisor enamel as pauciserial. In 1985 (p. 481,482) he described it as “condition intermediate between pauciserial and multiserial.” Thomas Martin, Universitat Bonn, Germany(personal communication), October 11, 1990 stated that Prolapsus has pauciserial enamel. Pearce-Sellards Series No. 48 41372-782(Wood’s-241G),RI 1;-256,LM 1;-262,RM';-285,RM 1;-300,LM 1;252,RM2; -263,LM2;-295,RM 2;-304,LM2;41672-3,skullfragmentwithRP4-M',LP3alveolusofP4 - Ml lingualhalfofM 2 -11,skullfragmentwithRLI,RP3-M2;-93,RM'-M2; ,41443-70,LM 1 , orM 2;41745-40,RP4;-31,RM 1orM 2;-60,RM 1orM 2;-134,RM 1orM 2;-147,LM'orM 2; -282,RM 1orM 2;-283,RM 1orM2;-284,RM 1orM2;-285,RM 1orM2;-286,RM 1orM 2; -289,LM 1orM 2;-290,LM 1orM 2;-292,LM 1orM 2;-294,LM'orM 2;-295,RM 1orM 2; -297,RM 1orM 2;-298,RM 1orM 2;-299,LM 1orM 2;-300,LM'orM 2;-301,LM 1orM 2; -302LM 1orM 2;-303,LM 1orM 2;-305,LM3;41549-3,RM 3;42953-6,LM 1orM 2. - Stratigraphic position. Lower member of the Devil’s Graveyard Formation, basal Tertiary conglomerate (41443), Whistler Squat quarry (41372), Agua Fria area; Hannold Draw area. Big Yellow Sandstone Member, Canoe Formation, Crusher Section, Big Bend National Park (42953). Middle member Devil’s Graveyard Formation, Purple Bench locality (41672), Serendipity locality (41745), Margaret’s Bonebed (41549), Agua Fria area. - Description. ThemesoconidsonP.sihilatorisfromtheSerendipityandPurpleBench localities show more variability than those from the Whistler Squat quarry. From the former localities it is usually a single but lophate crest with only three out of 24 specimens showing double cusps. The lophate mesoconid may show a short and weak connection with the protoconid; it may also have a short, weak connection with the hypoconid or the hypolophid, or it may not connect with any other cusp. On the M 3 the mesoconidconnectswiththeentoconidon threespecimensanddoesnotconnectwith the entoconid on three others. Of seventeen isolated lower first or second molars from Serendipity locality, 12 have a complete hypolophid with no hypoconulid, two have a very small hypoconulid on complete hypolophids, two have incomplete hypolophids with no hypoconulids, and one has a complete hypolophid with a hypoconulid. Obviously, the abovecharactersarevariablewithinasamplefromonelocality. Thehypoconulidisrare on specimens from the Serendipity locality. The connection of the crest from the entoconidtothemesoconidispresent inthreeof24teethfromtheSerendipityand PurpleBench localities. Thetypelowerjaw,41372-179,doesnothaveaP4. Wood(1973)usedaP4ofP.junctionis(41444-1) and a fragment of a P4 of P. sihilatoris (41372-299) for the basis of his description. AnuneruptedP4ispresenton41672-106(fig. 1)andafullyeruptedoneon -198. There is an anterior cingulum on the P.junctionis P4 (41444-1) but there is only a very short anterior cingulum and an anteroconid on each of the same teeth at the PurpleBench and Serendipity level. A hypoconulid is present on 41672-106; otherwise, the description ofWood (1973:24-25) is applicable to P. sihilatoris. AP3 is present on 41672-11 (figs. 2A, B, C) and is represented by alveoli on 41672-3 (fig. 3). ItissafetoassumethatskullsofProlapsusintheearlierWhistlerSquatlocalfauna would also have P3 although none is presently known. , It must be pointed out that in figure 8 of Wood (1973) the explanation for "F" was inadvertently omitted and should read: F. LP4 41444-26. Also in the same figure, H. 41443-30isnot aLM3ofProlapsusjunctionis, , butisfromthesameundescribedrodent as the P4 in figure 7. 1991 Prolapsus: Sciuravidae 5 On 41672-3 the internal portions of M 2 and M 3 are preserved. Although the M 3 is worn, thereisstill aprominentanteriorcingulumthatendslinguallyoppositethemiddleofthe protocone. In the undescribed rodent 41443-30 the anterior cingulum continues to the anterointernal corner of the tooth. On the M 3 of Prolapsus the protocone is separatedfrom the hypocone by a median valley, as in M 1 and M 2, and is still present on the worn tooth. The hypocone is a prominent cusp. An isolated M 3, 41745-305, is referred to P. sihilatoris and is the basis for the following description. The M 3 ofP. sihilatoris has a prominent anterior cingulum that has its lingual end at the anterobuccal corner of the protocone. The protocone is larger than the hypocone and separated from it by a prominent valley. The internal valley is also present on 41672-3 where only the internal half ofM 3 is preserved. The protoloph is complete in 41745-305 but this is a slightly worn tooth so it is not possible to distinguish a protoconule. The metacone is small compared to the paracone. A short loph extends from the position of the metaconule to the posterior cingulum enclosing a posterolingual basin. Specimen41745-305 does not have nearly as complicated a pattern as 41443-30 that was identified as the M 3 of Prolapsus by Wood (1973;fig. 8H). Prolapsus junctionis Figures 4, 5, Tables 5-8. - Type. TMM 41444-62, isolated RMj. - Material. TMM41444-1,RP4;-116,LMj;-59,LM2;-61,LM3;75,LM3;41443-363,RP4; -433,LP4; -33,LM,; -68,RM,; -71,LM,; -75,RM,; -141,RM,; -222,RM,;-371,RM,; -381,RM,;-417,RM,;-491.RM,;-496,RM,; -507,RM2;-557,RM2;-566,LM2; 41745 -471,LM,;-472,LM,;-277,LM2; -322,LM2;-273,LM3;-276,LM3;-279,LM3;-280, LM3; 42952-103, RP4; -82, LM,; -83, LM,; -81, RM, or M 2; -80, RM, or M 2; 41444-187 (Wood’s-568),LI1;-26,LP4;-69,LM 1orM 2;-104,LM 1;-115,LM 1;-25”,RM2;-164, RM2;-168,LM2;41443-545.RdP4;-560,LdP4;-66,LMF-434, RM 1orM2;-529,RM 1 orM 2;-54,LM2;-65.RM2;-73,LM2;-74,LM2;-78,LM2;-215,RM2;-324,RM2;-396, 1 11 RM2;-542,RM2;-445,RM3;41745-72,LM 1;-136,LM orM 2;-269,LM ;-270.RM ; -110,LM2;-266.LM2;-267,LM2;-366,LM3;42952-67,LM 1;-68,LM1;-69.RM 1;-70, RM ;-73,LM 1orM 2;-74,RM 1orM 2;-71,LM2;-72.RM2;42953-7,RM 1orM 2. 1 - Stratigraphic position. Lower member of the Devil’s Graveyard Formation, basal Tertiary conglomerate (41443, 41444), Agua Fria area; Dogie Mountain (42952); middle member of the Devil’s Graveyard Formation, Serendipity locality (41745), Agua Fria area. - Emended diagnosis. Smaller than P. sihilatoris. Mesoconid prominent and lophate; hypolophid extends toward hypoconid in earlier members of species and connects in Serendipity members; entoconid may connect to posterolophid; pseudomesoloph extends fromthehypocone tonearthecenteroftheuppermolars,mesostylesmall;protostylenot a distinct cusp. Pearce-Sellards Series No. 48 - Description. Size is the main distinction between P. sibilatoris and P. junctionis. The scatter diagrams in figures 4 and 5 imply that there are two distinct populations. I here is no apparent change in size within either the large or the small group upward in the section. However, P. junctionis is much more abundant in the basal Tertiary conglomerate; onlyasingletooth,41443-70LM 1orM 2,isidentifiedasP.sibilatoris.Thelatteroccurs only at the Whistler Squat quarry level. Thetwospecies arenotasdistinctmorphologicallyattheWhistlerSquatlevelasimplied by Wood (1973), who described Prolapsus sibilatoris, the larger species, as having well developed mesoconids, complete or nearly complete hypolophids, complexities in the upper cheek teeth and a well developed pseudomesoloph. AccordingtoWood(1973),thesmallerspecies, P.junctionis,has mesoconidsthatextend less than half-way across the lower teeth, hypolophids that are never complete, and entoconids that may connect to the posterolophid. The pseudomesoloph is broadlyinterrupted in the center of the upper molars, the mesostyle is small, and the protostyle is a distinct cusp. Additional differences noted in this study are that the mesoconid in P. sibilatoris usually occurs as two slightly separated cusps that connect with wear, while themesoconidofP.junctionisiseitherasingle cusp or, morecommonly, acompleteloph. In addition, some specimens of P. sibilatoris have a small cusp partially separated from, and located immediately lingual to, the metacone. Although these character distinctions are valid in general, they are not consistently present in the sample. The morphologic similarities between these two species are more readily apparent than the differences, and a comparison ofM 2 in the types ofP. sibilatoris (TMM 41372-179) and P. junctionis (TMM 41444-59) demonstrates that some of these specimens are nearly identical. The mesoconid does in fact extend further than half the widthofthelowermolars insomespecimensof P.junctionis(e.g.,LM2TMM41444-59). The mesoconid ofP. junctionis in TMM 41443-557 (RM2 ) extends to nearly one half the lengthofthetooth,andthehypoconulid iscomplete,althoughitnarrowsandshallowsas it approaches the entoconid; this condition is seen in most of the P. sibilatoris specimens as well. The hypolophid is no more complete on P. sibilatorisM 2 (e.g., TMM 41372-179 and TMM 41372-266) than is the hypolophid of that tooth in most specimens of P. junctionis. The M 2 ofP. sibilatoris (TMM 41372-295) and P. junctionis (TMM 41444-168) also shows the similarities between the two species. The mesostyle is not consistently larger in P. sibilatoris specimens. The extension of the pseudomesoloph and the prominence of the protostyle are highly variable in both species. Although the size bimodality (figs. 4 and 5) remains distinct, specimens from higher in thesectiondisplaysubtlechanges inthetoothmorphologyofbothspeciesthatresult in anevengreatersimilaritybetweenP.sibilatorisandP.junctionis.In theuppermolarsof both species the pseudomesoloph, extending from the hypocone, is more pronounced and extends further toward the central part of the tooth. The mesostyle is generally absent or quite small; the protoloph is better developed, and fully or nearly connected to the paracone; the anteroloph is reduced, and the posteroloph and pseudomesoloph are more 1991 Prolapsus: Sciuravidae 7 pronouncedandfullyconnectedtothehypocone,forming aseleneintheposteriorlingualportion of the tooth. In the lower molars the mesoconid more commonly exists as a single cone in the earlier Prolapsus sample. It is positioned more lingually toward the center of the tooth and rarely connects with the hypoconid. The hypolophid becomes more pronounced in the later forms, and more fully connected to both the hypoconid and entoconid. The protolophid, although more pronounced, never connects with the metaconid and alwayslies posterior to it. The anterior cingulum of P4 is reduced. It mustbe stressedthatthesemorphologicdifferencesbetweenProlapsusfromthehigherstratigraphic levels and Prolapsus from the Whistler Squat level are generalities, and are not present in all specimens. Despite these changes the teeth of both species from the Serendipity level remain quite similar to those of the Whistler Squat level and are assigned to P. sihilatoris and P. junctionis principally on the basis of size. The nearlyidentical, though smaller, TMM 41745-266 {P. junctionis) from Serendipity and TMM 41372-295 (P. sihilatoris) from the Whistler Squat quarry locality demonstrate this similarity. Insummary,thebimodal sizedistributionofProlapsusteeth occursthroughoutitsknown stratigraphic occurrence, but the morphologic differences, initially subtle at the Whistler Squat level, are even more indistinct higher in the section as the tooth morphologies of thelargeandsmallspeciesconverge. However,despitethelackofmajormorphologicdifferences between the small and large species throughout the section, these two taxa should not be synonymized. At one time it was believed that the Serendipity-Purple Bench populations might represent a new species. But with the larger sample size from both levels the only way to distinguish this new species would be to know its stratigraphic position. We were reluctant to do this even though it meant the P. sihilatoris and P. junctionis are interpretedherein toberathervariableintoothmorphology,yetconservative sofar as majorchanges are concerned over a timespan of perhaps 3 million years. - Relationship. Prolapsus junctionis and P. sihilatoris are closely related. The smaller size, and overall lesser degree of development of the lophs and accessory cusps of the cheekteeth,suggestthatP.junctionisis themoreprimitiveofthetwospecies. TherarityofP. sihilatorisfrom thebasalTertiaryconglomerateattheAguaFria area suggests thatP. junctionisistheearlierspecies. However,theenvironmentofdepositionwasdifferentat the basal Tertiary conglomerate from that at the overlying Whistler Squat quarry, so the absence ofP. sihilatoris from the former locality could be attributed to an environmentally biased sample. Wood (1972, 1973, 1974b, 1975, 1977, 1981, 1983, 1984, 1985) has consistently described Prolapsus as hystricognathous, and based primarily on this character assignedProlapsus to the suborder Hystricomorpha, infraorder Franimorpha (Wood, 1975). Wood (1980:86) stated that Prolapsus was also hystricomorphous based on unpublished data (TMM 41672-11 on loan to Dr. Wood). In his original description of Prolapsus, Wood Pearce-Sellards Series No. 48 (1973) did not classify the faunule of rodents from the Agua Fria area of West Texas above the family level; Prolapsus was placed in “Family Indet.” In the following yearWood (1974:45) explained the dilemma as follows: “However, hystricognathy is clearly present in the middle Eocene genus Prolapsusfrom southwest Texas (Wood, 1972, 1973), in the late Eocene Protoptychus (Wahlert, 1973) and in the Eocene Guanajuatomys from central Mexico (Blackand Stephens, 1973); it is incipiently present in other North American Eocene rodents. Ifhystricognathy isadiagnostic characteroftheSuborderHystricognathi, theseNorthAmericanformsmustbeincluded, astheonly demonstrableEocene membersofthesuborder.Iftheyareruledout,hystricognathymust, asaresult, be a character that has evolved several times independently in the North American Eocene and it cannot be considered a diagnostic feature of any importanceuntil it is proven how many more times it evolved independently.” Wood (1975:78-79) proposed that: “Since none of the known North American Eocene hystricognaths seems to fit into the Hystricidae, Phiomorpha, or Caviomorpha (although Wahlert in 1972 tentatively placed the Protoptychidae in the Caviomorpha) a separate ancestral group is neededtoreceive theseforms,for which I propose thetermFranimorpha, new infraorder based on the name of the earliest known included genus. The Hystricognathimay thenbe dividedintofourinfraorders: theAfricanPhiomorpha, the South American Caviomorpha, the Old World Hystricomorpha, (presentlyrestricted to the single family Hystricidae), and the Franimorpha, presentlyincluding the Reithroparamyinae, Protoptychidae, Prolapsus and Guanajuatomys, but which 1 believe must also have been present in the Eocene of Asia.” In 1981 and 1984 Wood included the Cylindrodontidae in the Franimorpha but did not propose a family for Prolapsus. Of greater importance was the problem of accepting “the postulatethathystricognathyis avalidbasisforisolatingonegroupofrodentsasthe Suborder Hystricognathi, because hystricognathy is assumed to have originated only once in the evolution of the rodents, and, therefore, all hystricognathous forms are de scended from a single hystricognathous ancestor” (Wood, 1984:153). An opposing point of view was taken by Korth (1984) who denied that Prolapsus was fully hystricognathous. He (1984:7) stated: “The type specimen of Prolapsus sihelatoris (sic) TMM 41372-179 is not fully(sic) hystricognathous jaw as stated by Wood (1972, 1973). The angle of the mandible of Prolapsus is no more laterally displaced than that of the earlyEocenesciuravidKnightomys Gazin(1961). ThemandibleofProlapsusisveryrobustand thebreadth ofthemandibleismuch greaterthan thatofKnightomys, making the angle look more laterally displaced. Wood (1977, 1981) also stated that the skull of Prolapsus was hystricomorphous. However, the undescribed skull (IMM 41672-11) of Prolapsus on which Wood based his statement has beenexaminedandcomparedtotheskullofBridgerianSciuravus. Theinfraorbital foramina of these two genera are the same relative size and are clearlyprotrogomorphous.” 1991 Prolapsus: Sciwavidae 9 In his original description of Prolapsus Wood (1973:31) said: “Were only the teeth of Prolapsus known, there would be no problem in placing it in the Sciuravidae, but the completehystricognathyofProlapsus,afeaturenot evenhintedat inanyknown sciuravid, makes its allocation to the Sciuravidae impossible.” Wood clearly recognized the similarity of the dental pattern of Prolapsus to that of the sciuravids but chose to follow a classification based on his interpretation of the lower jaw structure. Theoriginalspecimen, thetypeofProlapsussihilatoris(41372-179), hasbeenexamined by several experts on fossil rodents and a majority agree with Wood that it is a hystricognathous jaw. They also agree with Wood and Korth that the teeth are sciuravid. R. W. Wilson (1986:168-169) reviewed “Problems in Hystricognathy” and stated that: “Further, neither is it necessary to assume that the possession of incipient, or even fullydeveloped, hystricognathy relates rodents to each other, and excludes relationship with others” (Wilson, 1986:168). We believe that it is unlikely that Prolapsus would develop the unquestioned sciuravid premolar and molar tooth pattern in parallel with contemporary forms to the north and be unrelated to them at an infraordinal level. We also believe that the family Sciuravidae, likeothermiddleandlateEocenerodentfamilies,wasrepresented inWestTexasandthat Knightomys huerfanensis is morphologically close to Prolapsus. Not only are the mesoconid, anterior cingula, P4, and hypocone of P4 very similar in both genera, but Knightomys and Prolapsus display the same degree of lateral displacement of the angular process in the lower jaws (Korth, 1984). Family Eomyidae Deperet and Douxami, 1902 Genus Aguafriamys new genus Etymology. “Agua Fria”ranch “mys” Gr mouse. - Type species. Aguafriamys raineyi. - Stratigraphic position. Skyline channels, base of Bandera Mesa Member, Devil’s Graveyard Formation (Stevens, et al., 1984). - Age. Early Duchesnean, sensu Wilson (1984). - Diagnosis. Larger than Protadjidaumo, Viejadjidaumo, Aulolithomys hounites, and Aulolithomys cf. A. hounites (Wood, 1974). Approximately the same size as Centimanomys, but P4 smaller. Teeth brachydont. Anterior cingulum compressed to metalophid and protoconid with almost no trigonid basin. Metaconid prominent with transversely elongate mesolophid. Metaconid connected by mures to protoconid and hypoconid. 10 Pearce-Sellards Series No. 48 Aguafriamys raineyi new genus and species Figure 6, Table 9b. - Etymology. For Robert W. Rainey, Chief Preparator, Vertebrate Paleontology Labora tory, Texas Memorial Museum, The University of Texas at Austin, field companion and advisor to professors and students. - Type. TMM41580-32,rightlowerjawfragmentwithP4-M2. - Stratigraphic position and age. As for genus. - Description. Surface weathering removed all of the bone of the lower jaw except for a smallfragmentbelowM,. Theincisorwasnotpreserved. ThecrownsofP4andM,were embedded in matrix in their natural position and later cleaned. The P4 was cracked and repaired, and the posterolingual part of the tooth is unclear. The protoconid and metaconid are close; the metaconid is higher and more anterior. The trigonid basin is almost obliterated. A small mesoconid is present and a short mesolophid extends transversely to themiddleofthetooth. Muresconnectthemesoconidwiththeprotoconidandhypoconid. The metaconid and entoconid are the highest conids on all teeth. The lophs from the protoconid and metaconid unite to form a strong transverse crest. A weaker crest is formed by lophs connecting the hypoconid and entoconid. The protolophid extends to the posterobuccal corner of the metaconid. The protolophid is broad, and together with a short metalophid almost completely fills the trigonid basin. There is only a slightindication of an anterior cingulum on the anterobuccal corner of M, and M 2. The protolophid passes posterior to the metalophid as in sciuravids. The hypolophid is complete. The posterior cingulum is connected to the hypocone. The mesoconid is prominent on Mj and M 2 and a mesostylid is present but not prominent. A mesolophidextendslinguallyfromthemesoconidtowardthemesostylid,butdoesnotreachit. There is a short buccal extension of the mesolophid from the mesoconid. - Discussion. The molar pattern of Aguafriamys strongly resembles that of Prolapsussibilatoris from Purple Bench. In the former the mesoconid is prominent, the mures connect with the protolophid, and the hypolophid and the mesolophid are more pronounced, but the basic pattern is essentially the same. If this is true, and our familyassignmentsarecorrect, thenAguafriamysaneomyid,seemstobederivedfromProlapsus, , a sciuravid. This was anticipated by Fahlbusch (1973, 1979). There is an even more striking resemblance to Centimanomys from the Chadronian of northeastern Colorado. The elongate pit that lies between the cingulum and the metalophid-protolophid in Centimanomysisnotpresent inAguafriamys. Wood(1974) describedAulolithomyscf.A. bounitesfromthePorvenirlocalfaunaoftheViejaarea. Inthisformthemolarsaremuch shorter,morenearlysquare,thaninAguafriamysandthereisaprominentseparate anteriorcingulum. IfWilson’s(1984)correlationofthestratigraphic sectionsfromtheAguaFria area to the Porvenir area is correct, the Skyline channels would be early Duchesnean and the Porvenir local fauna late Duchesnean. Thus Aguafriamys would be older than Aulolithomys cf. A. bounites. 1991 Prolapsus: Sciuravidae 11 Subfamily Yoderimyinae Wood 1955 Genus Yoderimys Wood 1955 Yoderimysyarmednew species Figure 7, Table 9a. - Etymology. For Earl Yarmer, Preparator, Vertebrate Paleontology Laboratory, Texas Memorial Museum,TheUniversityofTexasatAustin,askillfultechnician. - Type. TMM 42153-2, LP4-M3. - Referredmaterial. 42019-10,LMrM3. Tentativelyreferred; 42019-32,articulated skullandjawswithalveolusforP3 P4-M'(wornand/orbroken)Ij,P4-M3(concealedbybeing articulated), atlas and axis. , - Stratigraphic position. Approximately 60 feet (18.3 m) above base (road level) of Bandera Mesa Member of the Devil’s Graveyard Formation (Stevens et al., 1984:fig. 10),CoffeeCuplocalfauna(Wilson, 1986,fig.6),PresidioCounty,Texas. - Age. Chadronian. Diagnosis. Aboutthesamesizeas Y.hurkei,whichisthelargestspeciesofYoderimys.P4 longer than- M,. M, to M 3 wider anteriorly than posteriorly. Protoconid and metaconid on P4 high. Trigonid basin of P4 open anteriorly, apparently without an anteroconid. Anteroconid prominent on Mj to M 3. Teeth brachydont, metaconid and entoconid high. P4 has a double mesolophid, each loop pointed lingually at right angles to the midline of the tooth row. The mesolophid originates from a lophid that connects the base of the metaconidwiththebuccalmarginoftheentoconid. Ahypolophidconnectsthehypoconidwith the entoconid. Posterolophids are prominent on all teeth. The anterior cingulumcloses off a trigonid basin lingually. A continuous loph zig-zags from the anterocone, only slightly buccal to the anteroposterior center of the tooth row, to the lingual base of the hypocone where it turns linguad to form the posterior cingulum. On M, a small mesolophid is directed toward the entoconid, on M 2 a small mesolophid forms a loopenclosing a lake at the base of the metaconid, and on M 3 the metalophid is directed toward the entoconid. With a larger sample this structure probably would be variable. - Description. Metaconidsandentoconidsarehigh.ThemolarpatternisH-shaped,with connected protolophids-metalophids and hypolophids forming transverse lophs and an equally high loph passing longitudinally from the anterocone to the hypocone and the posterior cingulum. There are deep valleys between the lophids. An accessory lophid on the anterolingual side of the mesoconid is directed toward the metaconid or the hypoconid, or, as on the M, of the type, it forms a closed lake. On 42019-10 M, is too worn, the accessorylophidofM2isdirectedtowardtheentoconid, andon M 3itisclosedtoforma loph. The skull and lower jaws (42019-32) were tentatively identified as Yoderimys sp. by Wood (correspondence to J.A.W.), who skillfully prepared them from a single nodule. The alveolus for a P3 is highly suggestive of Yoderimys. Pearce-Sellards Series No. 48 - Discussion. Unfortunately, not enough of the lower jaw is preserved on either of the Texas specimens to be compared with Y. burkei. The measurements of the teeth, however, show that they are approximately the same size. The accessory lophs on the type of Y. yarmeri seem to be more elaborate than on Y. burkei. There are two on P4one directed , toward the metaconid. a closed loop on M 2, and one on M 3 which is directed toward the entoconid. The teeth are longer than those of Y. lustrorum (see Table 9a), and the posterior cingulum reaches the posterior lingual corner of the tooth in Y. yarmeri. 1991 Prolapsus: Sciuravidae 13 REMARKS ON THE FAMILIES SCIURAVIDAE AND EOMYIDAE The early history of the genera and species belonging to the family Sciuravidae was well covered by Wilson (1938) and does not need to be reviewed here. In the same article Wilson (1938:127-128) clearly described the dental characters of the genus Sciuravus. SincethattimeWasatchianspecieshavebeenreferredtothegenusKnightomysGazin 1961 from the San Jose Formation of the San Juan Basin, New Mexico (Flanagan, 1986), and from Wyoming and Colorado. Pauromys sp. was identified by Korth (1984) from the WasatchianWindRiverFormationofWyoming. Thefamilyisbetterknown innumbers of taxa as well as number of individuals in the Bridgerian of Wyoming and particularly at Powder Wash, Utah (Dawson, 1968). Early Uintan species are known from the Uinta Basin of Utah (Dawson, 1966) and from San Diego County, California (Wilson, 1940; Lillegraven, 1977).ThefamilyiswellknownintheEoceneofNorthAmericabutisnot as well represented by skulls and jaws as one might wish. On the basis of dental characters Wood (1973:29) stated that; “The cheek teeth of Prolapsus seem clearly to be of sciuravid derivation.” We believe on the basis of dental characters that the cheek teeth of Prolapsus are sciuravid, and that Prolapsus should be assigned to the Family Sciuravidae. Prolapsus sp. ofWood (1973) was referred to the genus Pauromys by Walton (1986). These assignments expand the knowledge of the Family Sciuravidae and, we believe, assist in the search for the roots of the FamilyEomyidae. Storer (1987) described new material from the Duchesnean of Saskatchewan and reviewed the radiation of the Eomyidae. He reaffirmed the derivation of the Eomyidae from the Sciuravidae, with sciuravids resembling Knightomys of the Wasatchian, the ancestral form. In his figure 2 he divides the eomyids into three groups: the Yoderimys ” group,the“Namatomysgroupand theAdjidaumo-Paradjidaumogroup. Theseparation between the yoderimyines and other eomyids took place during the Bridgerian, and is based on his node 4 where the eomyids other than Yoderimys lost P3. Dawson (1968:fig. 41) illustrated a fragment of a maxilla of Pauromys with the anteriormost alveolus suggesting that P3 was absent. The same condition is found in another fragment of a maxilla ofPauromys,TMM40630-34,fromtheCandelarialocalfaunaoftheVieja area. Ifthisis “ correct, Pauromys would belong in Storer’s (1987) Namatomys group.” We would like to point out that no upper teeth nor maxillae are known for several of the taxa Storer (1987) referred to the Adjidaumo-Paradjidaumo group, and therefore the presence or absence of P3 is not known. Prolapsus, on the other hand, retains P3 and would therefore be along his line leading to Yoderimys. We would suggest, however, that his “node 2”, with the characters he notes, be raised to later in the Uintan at least so far as a sciuravid-eomyid transition in Texas is concerned. InProlapsus the muresfromthemesolophid arevariable incompletenessand direction and their position is lingual rather than medial. Aguafriamys is more like Prolapsus inthatthemesoconidismorebuccalbutthemuresarecomplete.Aguafriamys is from the Skyline channels, early Duchesnean {sensu Wilson, 1986). Unfortunately the upperdentitionofAguafriamysis notknown. 14 Pearce-Sellards Series No. 48 CONCLUSION Areexamination ofallmaterialofProlapsussihilatorisandP.junctionisleadsus toagree with Korth (1984) that Prolapsus should be included in the Family Sciuravidae on the basis of dental morphology. This assignment was considered by Wood (1973:29) but rejected because of the hystricognathous condition of the jaw fragment and the hystricomorphous condition of the skull (TMM 41672-11). Both conditions were disputedbyKorthbuttheirassessmentbyWoodisinprogress. Itcanbeconcludedfromour study that hystricognathy has occurred in Prolapsusa sciuravid, and therefore has occurred more than once. The most similarearlier taxon is, probably Knightomys huerfanensis, and the most closely related taxon is the eomyid Aguafriamys. We prefer to leave open the question of the classification ofProlapsus above the familylevel. Prolapsus was placed in the infraorder Franimorpha by Wood (1975) and in the suborderSciurognathibyKorth(1984). Thisisaproblembeyondthescopeofthispaper, thepurposeofwhich istosupplement theknowledge ofthegeographicandstratigraphic range of Prolapsus and to describe the complete upper and lower dentitions based on skull and jaw fragments collected since 1973. ACKNOWLEDGEMENTS We are grateful to Mr. and Mrs. Billy Pat McKinney, lessees, and Messrs. J. H. Burton and Macon Richmond, owners of the Agua Fria Ranch, who provided valuable assistance. The Purple Bench locality is on the upper reaches of the Alamo de Cesario on the ranchofDr.WalterW.DalquestofMidwestern StateUniversity,whogenerouslypermittedfield parties to collect vertebrate fossils from his land. Collecting in Big Bend National ParkwasconductedunderFederalAntiquitiesPermitNo.88Bibe-1(P). ParkNaturalists TomandBettyAlexandMikeFlemingwereparticularlyhelpful. Financialsupportwas provided to A. C. Runkel by the Wann and Marietta Langston Fund, the Howard Lowe Fund and the Owen Coates Fund of the Geology Foundation, The University of Texas at Austin. Dr. E. L. Lundelius, Jr., read the manuscript and his suggestions were most helpful. Drs. Mary Dawson, W. W. Korth and J. E. Storer reviewed the manuscript and offered constructive criticisms for which we are grateful. This is a contribution of the Vertebrate Paleontology Laboratory, Texas Memorial Museum, The University of Texas at Austin. 1991 Prolapsus: Sciuravidae 15 Figure 1.ProlapsussibilatorisWood1973,TMM41672-106,PurpleBench,Serendipitylocal fauna. A. occlusal view. B. lateral view oflcft ramus. 16 Pearce-Sellards Series No. 48 Figure 2. Prolapsus sibilatorisWood 1973. TMM 41672-11, Purple Bench, Serendipitylocalfauna.A. lateralviewofrightsideofskullfragment. B. occlusalviewofP3-M2. C. palatal view of skull fragment. 1991 Prolapsus: Sciuravidae 17 Figurc3. Prolapsus sibilatoris Wood 1973. TMM 41672-3, Purple Bench, Serendipitylocalfauna. OcclusalviewP4-M3. Figure4. Graphofthelength(L)versustheposteriorwidth(PW)ofMj and M 2 ofProlapsussibilatoris and P. junctionis from various sites in Trans-Pecos Texas. P. junctionis in capital letters, P. sibilatoris in numerals. Localities: A-l, 41444, 42953, basal Tertiaryconglomerate; B-2, 41443, basal Tertiary conglomerate; C-3, 41372, Whistler Squatquarry; D-4, 41745, Serendipity quarry; E-5, 41672, Purple Bench; F-6, 42952, DogieMountain. 18 Pearce-Sellards Series No. 48 Figure5.Graphoflength(L)versustheposteriorwidth(PW)ofM 1andM2LofProlapsussibilatoris and P. junctionis from various sites in Trans-Pecos Texas. Numbers and letters as in Figure 4., Figure 6. Aquafriamys raineyi new genus and species, type, TMM 41580-32. Occlusal view P4-M2 . Figure 7. Yoderimys yarmeri new species, type, TMM 42153-2. Occlusal view P4-M 3 1991 Prolapsus: Sciuravidae 19 PW 1.79 1.96 3M AW 2.12 2.12 L 2.28 2.15 PW 2.58 2.05 2.08 2.12 2.12 2.41 2.15 2.22 2.22 1.92 1.99 2.35 2.15 2.18 2.05 2.05 2.25 2.22 2.22 2.28 2.28 Texas. or2 1M AW 2.58 2.12 2.28 2.22 2.28 2.51 2.28 2.45 2.28 2.18 2.28 2.35 2.18 2.28 1.96 2.25 2.28 2.28 2.28 2.58 Trans-Pecos L in 2.45 2.18 2.28 2.15 228 2.45 2.09 2.35 2.28 2.15 2.31 2.25 2.12 2.22 2.15 2.09 2.28 2.22 2.18 2.18 sites PW 2.05 2.18 various MAW 2.28 2.61 from2 Wood2.18 2.28 PW 2.35 2.15 2.45 2.28 2.25 2.22 sibilatorisL 1 MAW 2.48 2.22 2.61 2.45 2.45 Prolapsus L of2.38 2.28 2.31 2.15 2.38 2.12 teethPW 2.12 2.15 1.99 upper 4 P ofAW 2.12 2.12 1.89 L 1.79 1.86 1.73 Measurements RL 1. Tabic41372-256 41372-285 41372-300 41372-295 41672-341672-341672-93 41745-40 41745-31 41745-60 41745-147 41745-282 41745-283 41745-284 41745-285 41745-286 41745-289 41745-290 41745-292 41745-294 41745-295 41745-297 41745-298 41745-299 41745-300 41745-301 41745-302 41745-303 41745-305 41549-3 42953-6 20 Pearce-Sellards Series No. 48 Table 2. Statistics on upper teeth of Prolapsus sibilatoris Wood from various sites in Trans-Pecos Texas. P4 M1 M2 M 1/2 M3 L n 3 6 2 20 2 X 1.79 2.27 2.23 2.23 2.22 SD 0.112 0.104 AW V(%) n 3 4.94 5 2 4.66 20 2 X 2.04 2.44 2.45 2.30 2.12 SD 0.141 0.148 PW V(%) n 3 5.76 6 2 6.43 21 2 X 2.09 2.28 2.12 2.19 1.88 SD 0.105 0.149 V(%) 4.60 6.80 1991 21 Prolapsus: Sciuravidae PW 2.25 1.73 1.86 2.18 2.05 2.02 M, AW 2.18 1.96 2.05 1.96 2.12 2.15 L 2.93 2.61 2.67 2.61 2.93 2.58 Texas. Mior 2 AW L Trans-PecosPW in sitesPW 2.45 1.89 2.18 1.96 2.18 2.12 various m2 AW 2.25 1.86 2.12 1.79 2.12 2.15from 2.45 2.25 2.54 2.45 2.38 2.61 Wood PW 2.22 1.96 1.96 2.09 1.96 2.12 1.96 2.28 sibilatorisL M, AW 1.99 1.76 1.83 1.79 1.73 1.83 1.79 1.79 Prolapsus L of2.35 2.35 2.54 2.35 2.31 2.48 2.45 2.61 teethPW 1.59 1.96 1.70 lower of P4 AW 1.24 1.30 L 1.96 2.28 Measurements 3. Table41372-179 41372-299 41372-284 41372-266 41372-143 41372-265 41372-269 41372-381 41672-8 41672-9 41672-14 41672-15 41672-85 41672-106 41672-198 2.02 2.22 1.63 2.09 2.12 1.83 2.54 3.19 2.61 2.02 2.35 1.96 2.18 2.02 1.99 1.92 2.18 1.92 2.12 1.96 1.86 1.96 1.63 2.02 1.99 1.79 1.70 2.12 1.66 2.02 2.12 2.22 2.61 2.45 2.45 2.45 2.25 2.55 2.45 2.41 2.48 2.41 2.09 1.76 2.38 1.92 1.53 2.25 1.53 1.27 1.92 41745-84 41745-272 41745-273 41745-277 41745-316 41745-371 41745-89 41745-142 41745-278 41745-307 41745-308 41745-310 41745-314 41745-315 41745-317 41745-318 41745-319 22 Pearce-Sellards Series No. 48 Table 4. Statistics on lower teeth of Prolapsus sibilatoris Wood from various localities in Trans-Pecos Texas. P4 m2 M 1/2 m3 L n 3 10 6 11 9 X 2.05 2.39 2.47 2.42 2.74 SD 0.121 0.091 0.129 0.222 V(%) 5.08 3.68 5.33 8.12 AW n 3 10 6 11 9 X 1.27 1.79 2.03 1.90 2.05 SD 0.116 0.204 0.179 0.113 PW V(%) n 4 6.46 10 10.07 6 9.42 11 5.53 9 X 1.73 2.04 2.16 2.03 2.00 SD 0.134 0.162 0.101 0.21 V(%) 6.57 4.49 4.98 10.86 1991 Prolapsus: Sciuravidae 23 PW 1.63 1.60 4dP AW 1.63 1.60 L 1.63 1.66 PW 1.96 Texas. AW 2.02 L 1.99 Trans-Pecos3M in PW 2.05 1.96 1.79 1.73 lor2MAW 2.02 2.05 2.02 1.76 localities L 1.89 1.99 1.86 1.63 various PW 1.79 1.73 1.92 1.79 1.99 1.92 1.73 2.02 1.70 1.76 2.12 1.86 1.73 1.79 1.70 1.80 1.85 from Wood2MAW 1.89 1.96 1.86 1.86 1.96 1.76 2.09 1.96 1.86 2.22 1.96 1.56 1.83 1.53 1.85 2.11 L 1.83 1.86 1.79 1.96 1.96 1.86 2.05 1.92 1.96 1.96 1.83 1.76 1.79 1.76 2.09 1.98 junctionis PW 1.73 1.86 1.79 1.83 1.92 1.70 1.85 2.01 2.11 1.62 Prolapsus 1MAW 1.66 1.96 1.89 1.96 2.09 1.76 1.91 1.94 2.00 1.59 L of1.83 1.89 1.70 1.92 2.08 1.89 teeth1.79 1.83 1.89 2.10 upper PW 1.56 of 4 P AW 1.76 L 1.40 Measurements 5. Tabic41444-26 41444-69 41444-104 41444-115 41444-25 41444-164 41444-168 41443-434 41443-529 41443-545 41443-560 41443-66 41443-54 41443-65 41443-73 41443-74 41443-78 41443-215 41443-324 41443-396 41443-542 41443-445 41745-72 41745-136 41745-269 41745-270 41745-110 41745-266 41745-267 42952-67 42952-68 42952-69 42952-70 42952-71 42952-72 24 Pearce-Sellards Series No. 48 Table6. StatisticsonupperteethofProlapsusjunctionisWoodfromvarioussitesin Trans-Pecos Texas. dP4 p4 M1 M2 M1/2 M3 L n 2 1 10 16 4 1 X 1.65 1.40 1.89 1.90 1.84 1.99 SD 0.122 0.102 AW V(%) n 2 1 6.61 10 5.38 16 4 1 X 1.62 1.76 1.88 1.89 1.96 2.02 SD 0.157 0.179 PW V(%) n 2 1 8.38 10 9.46 17 4 1 X 1.62 1.56 1.84 1.84 1.88 1.96 SD 0.145 0.122 V(%) 7.92 6.64 1991 Prolapsus: Sciuravidae 25 PW 1.70 1.66 1.47 1.73 3 mAW 1.70 1.83 1.79 1.60 Prolapsus 2.02 2.38 2.45 2.28 Trans-PecosTexas. or 2 AW L PW junctionisWoodfromm2variousAW sitesin M, AW PW L PW 1.63 1.30 1.82 1.47 2.41 1.79 1.66 1.47 1.43 1.30 1.63 1.56 1.53 1.53 1.40 1.40 1.53 1.79 1.53 1.60 1.76 1.63 1.73 1.50 1.79 1.80 1.53 1.27 1.99 2.15 2.02 2.02 2.05 1.30 1.70 1.70 1.70 1.92 1.56 1.86 1.86 1.92 1.73 1.47 1.45 1.70 2.09 L of2.01 1.70 1.99 1.92 1.86 2.05 1.92 1.96 1.99 2.09 2.12 2.05 1.93 teethPW 1.56 1.37 1.56 1.68lowerP4 of AW 1.30 1.04 1.34 1.41 1.66 1.60 1.63 1.98 Measurements 7. Table41444-1 41444-62 41444-116 41444-59 41444-75 41443-363 41443-433 41443-33 41443-68 41443-71 42952-103 41443-75 41443-141 41443-222 41443-371 41443-381 41443-417 41443-491 41443-496 41443-507 41443-557 41443-566 41745-471 41745-472 41745-322 41745-276 41745-279 41745-280 42952-82 42952-81 26 Pearce-Sellards Series No. 48 Table 8. Statistics on lower teeth of Prolapsus junctionis from various sites in Trans- Pecos Texas. P4 M, m 2 m3 L n 4 13 7 4 X 1.72 1.97 2.10 2.28 SD 0.109 0.145 AW V(%) n 4 5.56 13 6.89 6 4 X 1.27 1.48 .69 1.73 SD 0.127 0.207 PW V(%) 4 8.56 14 12.31 8 4 1.54 1.63 1.74 .64 0.159 0.160 9.78 9.22 1991 Prolapsus: Scinravidae 27 PW 1.43 1.90 2.00 m3 AW 1.55 2.10 2.10 L 1.83 2.60 2.70 PW 1.80 1.68 1.81 2.0 1.64 1.60 2.00 1.90 m2 AW 1.73 1.64 1.76 2.0 1.71 1.63 2.10 2.00 W 2.40 L2 1.94 1.92 1.82 2.3 1.78 2.0 1.76 2.30 2.10 mPW 1.54-1.92 L 1.78 6.74 9 PW 1.75 1.57 1.9 1.57 1.80 1.90 2.60 AW 1.60 1.46 1.8 1.48 1.90 1.80 lor2 AW 1.48-1.88 M9 W 2.20 1.70 7.60 eomyids. L 1.97 1.90 2.3 1.85 1.6 1.76 2.21 2.10 M, L L variousPW 1.73 1.66 1.53 2.0 1.65 1.32 2.50 1.99 1.70-2.156.53 11 of (1978) 4 AW 1.43 1.37 1.32 1.7 1.35 1.12 PW PW 1.80 1.99 statisticsL 4 Slorer1.84-2.38 11.065 and2.05 1.96 1.87 2.3 2.02 1.6 1.82 2.30 n.sp. P Creek M3 L 2.00 P4AW 6 P4-7.51 7.80 6.9 9.00 n.g.Calf1.60 1.50-1.899.38 Measurementsraineyi L c. b., (TYPE) n.g.nsp. (TYPE) (TYPE) steward2.12-2.34 404 426 432 2.24 a.,4 53305325 5326 PM PM PM 9 Yoderimys bumpi burkei 9782 lustrorum yarmeri42153-242019-10 Aguafriamys41580-32Yoderimys Y. Tablea.Y.SDSMSDSMSDSMCM FMNHY. FMNHFMNHY.TMMTMMb.TMMc.M OR cv X 28 Pearce-Sellards Series No. 48 REFERENCES Black, C. C. 1968. Fossil mammals from Montana, Pt. 2. Rodents from the early Oligocene Pipestone Springs local fauna. Annals of Carnegie Museum 38:1-48. Black, C. C., and J. J. Stephens, 111. 1973. Rodents from the Paleogene of Guanajuato, Mexico. Occasional Papers, The Museum Texas Tech University Number 14:1-10. 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