EarlyPaleocene vertebrates, stratigraphy and biostratigraphy,West Fork of GallegosGanyon, SanJuan Basin, New Mexico bySpencer G. Lucas,Department ofGeology, University of New Mexico, Albuquerque, NM87131
Introduction U.S. Bureauof Land Managementcollected mudstoneand sandstonedetritus locallyde- There are only three well known areasin in this area (Kues and others, 1977). rived from the Nacimiento Formation (Qal, and of Wells, 1982,fig. 101).However, the San |uan Basin where early Paleocene This paper reports the fossil vertebrates Qal, (Puercan)vertebrates occur in the lowermost collectedbv this field partv. establishestheir the Oio Alamo Sandstonedoes form the re- strata of the Nacimiento Formation. These stratigraphicprovenance, ind discussestheir sistanibedrock under the plateauincised by areas,Betonnie Tsosie Wash, Kimbeto Wash, biostratigraphicsignificance. AMNH refers GallegosCanyon and its tributaries, and it and the headlandsof De-na-zinand Alamo to specimensin the Department of Verte- is exposed approximately 1 km (0.5 mi) Washes(Fig. 1), were already known when brate Paleontology,American Museum of northwest of the head of the WestFork (Ree- Sinclairand Granger(1914) published the re- Natural Historv; UNM refers to snecimens side, 1924,p. 30, pl. 1). This relationship to sults of two field seasons (1912-1913) of in the Departmentof Geology,University of the Ojo Alamo Sandstoneand the occurrence stratigraphicand paleontologicstudies of the New Mexico. of Puercanmammals indicate that the Na- strataexposed here are of the lower Paleoceneof the San Juan Basin. However, cimiento Sinclairand Granger(1974, p.315) did men- Stratigraphy -oart of the formation. tion a fourth occurrenceof Puercan verte- More than 37 m (l2I ft) of the Nacimiento The exposedNacimiento Formation con- bratesin the headlandsof the West Fork of Formation are exposedin rugged badlands sists of mudstone (63%), sandstone(33Vo), GallegosCanyon (Fig. 1). The only verte- at the headof the WestFork of GallegosCan- silcrete(3Vo), and siltstone(1%). These strata bratesthey reported from this locality (their yon (Figs.2, 3, 4).TheOjoAlamo Sandstone, can be consideredin three parts (Fig. 4): localitv4) were two teethof the Puercanmul- which underlies the Nacimiento Formation LowER MUDSTONES AND srLCRETns-The lower 16.5m (54ft) of sectionD (Fig. 3) and titubeiculate " Polymastodon"(: Taeniolabis).throughout the San Juan Basin (Baltz, 1,967), No additional vertebrateswere collectedfrom is not exposedhere (Fig.2). Instead,the base correlatedunits of sectionsA-C (Fig. 3) con- the West Fork of Gallegos Canyon unlil1977 of the Nacimiento Formation is coveredby sist of variegatedbands of red, green, buff, and gray mudstone intercalatedwith thin, when a field party under contract with the Quaternaryalluvium that consistsmainly of resistantsilcretes. Some of these strata, es- peciallythe silcretes,are laterallycontinuous for more than 1 km (0.6 mi) and thus allow a securecorrelation of sectionsB-D (Fig. 3). The silcretesare gray (but weather to yellow- brown), well-cemented,fine-grained, silica- rich layers (Rains,1981). MEDTALsANDSToNE courlnx-A thick (up to 14m; 46 ft) and complexsequence of sand- stone and clayey sandstoneforms a promi- nent part of the Nacimiento Formation exposedhere (Fig. 3). Most of the sandstone is gray-white, trough crossbedded,fine grained, and quartzose.However, two thin but distinctivehorizons of black,fine- to me- dium-grainedsandstone are present,one near the base and the other near the top of the sequence(Figs. 3, 5). Sinclair and Granger Q91a, p. 305) attributed the black color of this type of sandstoneto the presenceof manganeseoxide, but it seems likely that iron oxide also contributesto the black color and high density.Whether the formation of these black sandstones was a syndeposi- tional or diageneticevent is unclear,and their genesisneeds further study. The baseof the entire sandstonecomplex is an erosionalsurface of low relief (Fig. 3). At or near this base,fossil logs up to L m in diameterare common (Fig. 6), and other fos- sil logs and wood fragments occur sporad- icallythroughout the sandstonecomplex. All fossil vertebrate occurrencesin the Naci- miento Formation at the head of the West Fork are in the sandstonecomplex and are associatedwith the blacksandstone horizons (Fig.3). In fact,many of the vertebratefossils FIGURE 1-Location map of study area, San Juan County, northwest New Mexico. The colored circles collectedare encasedwithin the black sand- indicatelocations of Pueicancollecting areas in the NacimientoFormation. stone (Fig. 7D).
August 1984 Nao MexicoGeology UPPER MUDSTONES/ SANDSTONES/ SILCRETES, ANDsrLTSroNps-In this area,the upper part of the Nacimiento Formation consisti of deeply weatheredgray, green, buff, and black mudstoneand lesseramounts of sandstone, silcrete,and siltstone (Fig. 3). A thick, brown, medium-grained,and subarkosicsandstone is presentat the top of the exposuresin the northeastpart of the headlands(Fig. 3, sec- tion A). A prominent erosionalunconformity sep- arates Quaternary (and late Tertiary?) d^e- posits from the underlying Nacimiento Formation. These deposits are stable pedi- ment and terracedeposits capped by eolian sands (QTP1,;of Wells, 1982, frg. 1.0t).
Vertebratepaleontology Twenty-one localities in the Nacimiento Formation at the head of the West Fork of GallegosCanyon (Fig. 2) have producedver- tebratefossils representing the fish, reptile, and mammal taxa discussedbelow. ClassOsrrrcHrHyES Huxlev, 1880 Family LEprsosrsrperCuviea 1825 Genus and speciesindeterminate An incompletegar scale(UNM B-400c)and two gar scales(UNM 8-388) were FIGURE2-Geologic map collected of the headlandsof the west Fork of GallegosCanyon, from SanJuan Counry, New Mexrco. localities358 and 349, respectively. ClassRrpulra Linnaeus, 1758 Order TEsruorlps Linnaeus, 1758 Genus Asprotnnns Quoternory Hay, 7904 Aspideretes deposils sp. UNM 8-385, a nearly complete but frag- mented carapace(locality 347) is assignedio Aspideretesbecause it has eight pairs of cos- tals and the ridge-and-pit ornamentation upper mudslones, characteristic soodsiones, of this genus. Six speciesof si cretes ond Aspideretesare recognizedfrom the Puercan silistones of the Sanfuan Basin(Gilmore, 1979, pp.56- / 62;Matthew, 1937,p. 332),and the genus is in need of revision. Becauseof this, no spe- cies-leveldetermination of UNM 8-385 is'at- Lo*", verlebrotes ] tempted. UNM 8-1082 (locality 1037)consists of shell fragmentsidentical Mediol sondstone to thoseof UNM complex 8-385. Fossilmommcls ond owervertebrotes Genus and speciesindeterminate (/ocolities34\345, 348,349,35O,35t, Undiagnostic turtle-shell fragments 354,357, 358,36O, and other postcraniawere observedbut not col- lectedat localities345, 346, 347, 348, 349, 352, 353,355, 358, L037,1038, and 1039. Order Eosucnra Broom, 1914 Genus Cueupsos.qunusCope, 7877 Champsosaurussp. UNM B-381a(locality 344) is a small. am- phiplatyan vertebralcentrum. This centrum Unconsolidoied T-:-l Mudstone has a ventral keel, ' ' Sond F::=i a circular cross section, slightly concave li-..,----Illsondrton"fllllllllll.',^.^,^ sides, a large neurocentral t!"".":,,""" sutureon its superior surface,parapophyses I that areconfluent with the diapophyses,and F:rJ sittsrone a slight dorso-ventral compression poste- riorly. Clearly,this small (length : t4 mm) FIGURE 3-correlation of measuredstratigraphic sections of the lower part of the centrum is an anterior dorsal centrum of Nacimiento Formation in the headlandsof"thi west Fork or crii"g;, eu'nyon,---'r-" sun Champsosaurus,but it is inadequatefor a spe- JuanCounty, New Mexico.See Fig. 2 for locationof each,".tio.r.'-- cies-levelidentification (Erickson, 1972).-G.
Nm MexicoGeology August'l9M Order Cnocoorr-n Gmelin, 1788 (locality 349); 8-396, teeth (locality 353); B- Genus Lnoyosucuus Lambe, t907 Genus AuocNaruosucHus Mook, 1921 398a,partial skull (locality354);B-400a, par- ?Leidyosuchussp. Allognathosuchusmooki Simpson, 1930 tial lower jaw (locality358); and B-1086,teeth (locality1039). Storrs and others (1983)described UNM B-401a (locality360), the oldest known en- UNM 8-1121 (locality 351) is a fragmen- docastofan eusuchiancrocodilian. Based on lower jaw still bearing one globoseand tary skull fragments of UNM V407a, they ten- tooth. The anterior part of this lower striated tatively identified this specimen as Leidyo- bearsthree alveoli followed bv a much iaw suchus.The bicarinate,conical teeth and skull iargeralveolus, which, in turn, is'followed fragmentsof UNM 8-1083(locality 1037) also four much smalleralveoli. The diameters by may pertain to Leidyosuchils.If these identi- theseeight alveoli(5, 4.5, 4.4, 1.25,5.5, of fications are correct, they represent the first 4.5, and 4.0 mm from front to back) are 5.5, report of Leidyosuchusfrom the Puercan of somewhatgreater than thoseof AMNH 6780, the San Basin. the holotype of A. mooki(Simpson, 1930, p. fuan 7), but otherwisethe UNM andAMNH spec- Genus and speciesindeterminate imens are identical.Assignment of UNM B- 1121to A. mookithus seemscertain. Other Undiagnostic crocodilian remains were specimensfrom the West Fork of Gallegos observedbut not collectedat localities344, Canyonthat probablypertain to A. mookiare: u5, 346, 349, 352, 353, 355, 356, 358, 359, UNM 8-382, teeth (locality 344);8-387, teeth FIGURE6-Fossil los at baseof medial sandstone 1037,t038, and 1039.UNM 8-394 0ocalitv complexnear locality 1102,lower part of the Na- 351)is an eusuchianvertebral centrum, and cimiento Formation in the headlands of the West UNM 8-1085(locality 1038) is the distal por- Fork of GallegosCanyon. tion of a crocodiliantibia.
FIGURE 4-Badlands of the lower part'the of the Na- cimiento Formation, headlands of West Fork of Gallegos Canyon, in S1/2,sec. 15, T. 25 N , R. 72W L,lower mudstones and silcretes; M, medial sandstone complex; U, upper mudstones, sand- stones, silcretes, and siltstones.
FIGURE 7-Selected fossil mammals from the Nacimiento Formation in the headlands of the West Fork of CallegosCanyon. A, UNM V386, Taeniolabistaoensis,left Ml, occlusalview; B, UNM B-400b, Tae- FIGURE S-Black sandstone in medial sandstone niolabistaoensis, left I'?(?),lateral view; C, UNM V389, Desmatoclaenussp, left M{?), occlusal view; D, complex at top of measured stratigraphic section UNM B-401b,Desmatoclaenus sp., right Pr-Mr, occlusalview; E, UNM 8-397, Loxolophuspriscus, right C (Figs. 2, 3), lower part of the Nacimiento For- dentary fragment with partial Mt and complete M2 ,, occlusalview; F, UNM 8-392, Loxolophushyattianus, mation in the headlands of the West Fork of Gal- left dentary fragment with partial M1, completeMz, and nearly completeM:, occlusalview; G, UNM legos Canyon Rock hammer is 28 cm long V1,277, Loxolophuspentacus, left dentary fragment with Mt-r, occlusal view.
58 August 1984 NetuMexico Geology ClassMeruvALrA Linnaeus, 1758 TABLE l-Measurements (in mm) of lower molars of selected specimens of Loxolophus. L : maximum Order MUITTTUBERCULATACope, 1884 length, AW : maximum trigonid width, PW : maximum talonid width; * indicates an approximate Genus TarNrorears Cope,'1882 measurement of a worn or damaged tooth. Taeniolabistaoensis (Cope, 1882) Sinclairand Granger(191a, p.315) noted Specimen LAWPWLAWPW LAWPW that at the head of the WestFork of Gallegos L. priscus: "only Canyon two specimenswere fou--nd AMNH 3108 (holotype) 6.4 4.9 5.4 7-7 6.7 6.2 (both Polymastodon| : Taeniolabislteeth)." UNM 8_393 6.5 5.1 ^;- However,only oneAMNH specimen,1631,7, UNM 8_397 5.7 7.6 6.9 6.3 d.J 5./ 4./ a right dentary bearing M, of T. taoensis,is L. hyattinnus: Iabelledas having come from the West Fork AMNH 16343 5.5 3.7 4.3 5.8 4.6 4.7 6.7 3.8 3.6 of GallegosCanyon. Also, the recordof spec- UNM 8_392 4.6 6.2 5.5 5.4 6.5* 4.3 imenscollected by Sinclairand Grangeronly lists AMNH 76317from "ab't. 5 mi. N.W of Ojo Alamo Head of WestFork of Gallego[slc] Wash" (Grangerand others, 7913,p.2q. (Matthew, 7937,fig.2F., pl. 17,fig. 2). UNM onids on the Pr_oof UNM B-401b preclude Threespecimens of T. taoensisin the UNM 8-1087 (locality 1039)is a large (length : 7.1 assignmentto Oxyclaenussimplex, O. cuspi- : collection were found in the West Fork of mm, width 10.3mm), right M3that closely datus, and Loxolovhushaattianus-arctocvon- GallegosCanyon. UNM 8-381 (locality344) resemblesthe M3 of AMNH 954,a specimen ids in its size range. The only arctocyonidI is the posterior third of a left M. nearly iden- that Matthew(1937, pl. 13,fig.3) referredto have examined with Dremolars as molari- tical in size and morphology to AMNH 3046 as L. pentacus. form as those of UNM B-401b is Desmato- (Granger Simpson,1929, claenushermaeus from the Dragon local fauna and fig.8A). UNM Loxolophus 1888) 8-386 (Fig. 7A), from locality348, is a left M' rr,::;(Cope, of Utah (Gazin, 1941,fig. 19), which is much that is about the : larger than UNM B-401b. It is possible that same size (length 23.5 Loxolophushyattianus (Cope, 1885) mm; width : 17.7 mm) as AMNH 16305 the UNM specimenis a partial lower den- (Grangerand Simpson, 1929,p. 619).UNM Without documentation,Van Valen (1978, tition of the smaller,Puercan species of Des- 8-386 has 10 labial, nine medial, and 11 lin- p. 56) consideredL. priscusto be a synonym matoclaenus,D. dianae(Van Valen, 7978,p. gual cusps,as doesAMNH 970(Granger and of L. hyattianus.However, my examination 57). Nevertheless,until the lower dentition Simpson, 1929,hg.88) and is between the of AMNH and UNM specimensreferable to of D. dianaeis adequatelydescribed, I only 'tyoung" and "adult" stagesof wear defined these taxa reveals coniistent differencesin refer UNM B-401b to Desmatoclaenussp. forTaeniolabisby Grangerand Simpson(1929, size (Table 1) and morphology that justify UNM 8-389 (locality 349) is a left M'(?) figs. 3A-B). Finally, UNM B-400b Fig. zB), Matthew's (1937,pp.43,53) conclusionthat missing its labial edge (Fig. 7C). Like UNM from locality358, is a left tr(?)fragment with these speciesare distinct. The distinctions V401b, it appears to be an arctocyonid, but two accessorycuspules on its posterioredge. between L. priscusand L, hyattianusare re- it is difficult to identify becauseof its unusu- It probably pertains to Taeniolabis,although vealedwell by consideringthe threerelevant ally large hypocone and completelingual cin- it di+fjrsslightly from AMNH 16319(Granger specimens from the West Fork of Gallegos gulum. In sizeand morphology it most closely and Simpson,7929, fig.2A), which has only Canyon in the UNM collection. UNM 8-397 resemblesspecimens of Desmatoclaenuspro- one accessorycuspule on its posterior edge. (locality354) is a right dentary fragmentwith togonioides(compare with AMNH 3253; Cope, partial M, and complete M.. (Fig. 7E) as- 1884,pl. 25F, fig.17), although I have not Order CoNoyLARTHRACope, 18g1 signed here to L. priscus,as is UNIM 8-393 seen a specimen of D. protogonioidesthat Genus Pzrurrycuus Cope, 1881 (locality351), a right dentary fragmentbear- combines a complete lingual cingulum with Periptychuscoarctatus Cope, 1883 t-18M, and part of M,. UNM 8-392 (locality as large a hypocone as is present on UNM 351),on the other hand, is a left dentarv B-401b. Thus, identification of the UNM UNM B-398b(localiry 354)is a maxillarv bearing partial M,, complete M,, and nearly specimenas Desmatoclaenussp. seems rea- fragmentbearing partial ,. right Mr It clearlv complete M, (Fig. 7F) assignedhere to L. sonable. pertainsIo Periptychus, and the following fea'- hyattianus.V397 and 8-393 are larger than tures justify assignment to P. coarclatus: 8-392 (Table 1), their molar cusps are lower Genus and speciesindeterminate Mr2 are relatively wide linguolabiallv.their and more massive,their molars are broader hypoconesand piotostyles a"relingualio their (Table1), and, on V397, the M. is longerand UNM 8-1084 (locality 1038)is a fragmen- protocones,and their conulesare very small broader ("less reduced" ) than is the M, of tary but edentulousmaxillary about the size (seeMatthew, 1937,p. 123). v392. of Periptychus.UNM B-1088b(locality 1039) is Genus Crursolcuus Rigby, 19g1 UNM 8-391 (locality350) is the lingual half root and enamel fragments of a smaller Gillisonchusgillianus (Cope, 1882) of a right M' that closelyresembles"the cor- mammal, and UNM 8-384 consistsof post- respondingportion of the M'of AMNH 3121, crania fragments, including a partial tibia _ UNM B-1088a(locality 1039) is a right M,. the holotype of L. hyattianus,and AMNH comparablein size to the tibia of Periptychus. In size (length : 4.1 mm, rrigonid wiath : 1.6343,a specimenreferred to L. hyattianus 3.2 mm, talonid width : 3.1 mm) and mor- by Matthew (1937,p. 44, fig.lB). UNM B- Biostratigraphy phology it is identical to the M, of UNM 399(locality 35f is d right dentary fragment The occurrence of Taeniolabistaoensis, Per- 8-029, a partial skeleton of G. gillianus de- with roots of M, .; its close resemblanceto iptychuscoarctatus, Gillisonchus gillianus, Lox- scribedby Rigby (1981). 8-397 UNM supports provisional referral to olophuspentacus, L. priscus,and L. hyattianus L. prtscus. Genus LoxoropuusCope, 1885 supports assignment of the mammal-pro- Loxolophuspentacus (Cope, 1888) Genus DnsuerocresNus Gazin, 1941, ducing interval of the Nacimiento Formation Desmatoclaenussp. in the headlandsof the WestFork of Gallegos UNM 8-1271(Fig. 7c), from locality 1102, Canyon to the Puercanland-mammal "age" is a left dentary po fragment bearing roois of UNM B-401b(locality 360) is a right P.-M, (Wood and others, 1941;Russell, 1967).A and heavily -oll M._.. Its size (M, length : (Fig. 7D). This relatively small specimen(M, secondvertebrate-producing interval is pres- 9.1 mm, : trigonid width 7.3 mm, tilonid length : 6.0 mm, trigonid width : 4.5 mm, entT-9 m (23-29 ft) above this interval (Fig. width : 8.2 mm) and morphology are verv talonid width : 4.9 mm) appears to be an 3), but has only producedlower vertebratei. closeto those of AMNH 3i92 1M]'tengtn i arctocyonid with unusually molariform pre- Although assigningthis upper interval to the 9.3 mm, trigonid width : 7.5 mm, tilonid molars.Thus, the presenceof low but strbng : Puercanmight be doubted, data (Lucasand width 8.5mm), the holotype of L. pentacus paraconidsand metaconids and small tal-
New Mexico Geology Atglst 1,984 Schoch, 1982) indicate that Torrejonian (in- References cluding "Dragonian") horizons in the Naci- Baltz,E. H.,1967, Stratigraphyand regionaltectonic im- miento Formation are at least 50 m (164ft) plicationsof part of Upper Cretaceousand Tertiary rocks, east-centralSan Juan Basin,New Mexico:U.S. Geographicnames above Puercan horizons (Sinclair and Gran- GeologicalSurvey, ProfessionalPaper 552, 101 pp. U.S.Board on Geographic Names ge1 191,4;Lindsay Tomida, Cope, E. D., 7884, The Vertebrata of the Tertiary for- and others, 1981; km (20 mi) long, heads mations of the west: U.S. GeologicalSuwey of the Ter- Crystal Creek-stream, 32 L981),so it is likely that the upper vertebrate- in the Chuska Mountains in New Mexico near producing interval Fork ritoriesReport, Book 1, v. 3, 1009pp. along the West of Erickson, B. R., 1972, The lepidosaurian rcptile Champ- WashingtonPass at 36"05'04'N., 708"51'' 22' W., GallegosCanyon is Puercan. sosaurusrn North America: ScienceMuseum of Min- flows west into Arizona to join Cattail Wash at Historicallv. the occurrenceof Taeniolabisin nesota,Monograph 1, 91 pp the head of Coyote Wash 12.9km (8 mi) west the mammallproducing interval would be ac- Gazin,C. L.,7941, The mammalianfaunas of the Paleo- of Crystal, NM; Apache County, AZ, and San cepted as evidence cene of central Utah, with notes on the geology: Pro- County, NM; 36'04'52"N., 109"08'56"W.; that this interval pertains ceedingsof the U.S. National Museum, v. 91, pp. 7- Juan to the Taeniolabis,or upper, "zone" of the 1959 description revised; nof: Coyote Wash, Creek (BGN 1915). Puercan.However, in the headlandsof the Gi"li.o.", C. W., 1919,Reptilian faunas of the Torrejon, Simpson in the PeloncilloMoun- West Fork of GallegosCanyon, there is no Puerco, and underlying Upper Cretaceousformations Maverick Spring-spring, tains,3.5 km (2.2mi) north of Mount Baldy and mammal-producing interval to correspond of SanJuan County, New Mexico: U.S. GeologicalSur- vey, ProfessionalPaper 119, 58 pp. 9.9km (6.1mi) west of Eakins;Hidalgo County, to the Ectoconrrs, or lower, "zone" the Puer- of Granger,W., Olsen, G., Sinclair,W. J., and Martin, J., New Mexico;31'43'10' N., 108"55'50'W.;not: can. In Kimbeto and BetonnieTsosie Washes 1913,Record of specimens,New Mexico1913: Unpub- Mavarick Spring. the reverseis the case:an Ectoconus"zorre" lished report in Archives of Department of Vertebrate Spring Cteek-stream, 72.9km (8 mi) long, heads Paleontology,American Museum of Natural History, mammal-producing interval is not overlain at the iunction of Estufaand Las CuatasCreeks "zone" New York, 98 pp. on the south side of Stove Ridge in New Mexico by a Taeniolabis interval. Only in the the Granger,W., and Simpson,G. G.,1929, Arevisionof at 36'58'35"N., 106"44'20'W.,flows west-north- headlandsof De-na-zin and Alamo Washes Tertiarv Museum of Nat- Multituberculata: American River at Chromo, Colorado; are mammal-producing intervals represent- ural History, Bulletin, v.56, pp.601-676. west to the Navajo Archuleta County, Colorado, and Rio Arriba ing both "zones" present in a single strati- Kues,B. S., Froehlich,J. W, Schiebout,J. A., and Lucas, County, New Mexico; sec.9, T. 32 N., R. 1 E., graPnlc sequence. S. C.,1977, Paleontologicalsurvet resourceassess- ment, and mitiSation plan for the Bisti-Star Lake area, NMPM; 37'07'58'N., 106'50'45'W.;noi: Stove There are two alternate explanations for northwestemNew Mexico:U.S. Bureauof Land Man- Creek. the distribution of these Puerian "zones" in agement, Report to Albuquerque Otrice,1525 pp. StoveCreek-stream, 5.6 km (3.5mi) long, heads the SanJuan Basin: Lindsay,E. H., Butler,R. F., and Johnson,N. M., 1981, in Colorado on the north slope of Stove Ridge Magnetic polarity zonation and biostratigraphy of Late at 36"59'35" N., L06'44' 35' W., fl ows west-north- Cretaceousand Paleocenecontinental deposits, San Juan west through New Mexico to Spring Creek 5.6 1) The Taeniolabisand Ectomnus"zones" Basin, New Mexico: American Journal of Science, v. km (3.5mi) southeastof Chromo, Colorado;Ar- 281.,pp.390-43s. do represent successiveintervals of chuletaCounty, Colorado,and RioArriba County, Lucas,S. Puercan time. The absenceof fossil G., and Schoch,R. M., 1982,Early Paleocene 706'47'20' W. vertebratesfrom the West Fork of GallegosCanyon, a New Mexico; 37'00'73' N., mammalsrepresenting one the other Canyon-canyon, 3.2 km (2 mi) long, or "new" Puercan collecting area in the San Juan Basin, Tanbark zone in Kimbeto Wash, BetonnieTso- New Mexico: Geological Society o{ America, Abstracts headsat 3329'34' N ., 105"47' 76" W., trends south sie Wash, and the West Fork of Gal- with Programs,v. 14,p.320 to Bonito Creek, 19 km (12 mi) northwest of legos Canyon reflects inadequate Matthew, W. D., 1937,Paleocene faunas of the San Juan Ruidoso; Lincoln County, New Mexico; sec. 3, sampling, biased preservation, or Basin,New Mexico: Transactionsof the American Phil- T. 10S., R. 11E., NMPM;33'28'02"N., 705"47'06' osophical Society,v. 30, pp. 1-510. W. stratigraphic differences in the lower Rains, G. E.,7981.,Paleocene silcretes in the San (4 part Juan Taylor Draw-ravine, 6.4 km mi) long, heads of the Nacimiento Formation in Basin:M.S. thesis, University of Arizona, 81 pp. at the baseof theAnimas Mountainsat 31'31'15" ihese areas. Reeside,1.8., Ir., 1924,Upper Cretaceousand Tertiary N., 108"48'40'W.,trends southwestthen north- formations of the western part of the San Juan Basin, west to join FosterDraw at the head of Animas Survey, 2) These"zones" Colorado and New Mexico: U.S. Geological 0.48km (0.3mi) northeastof Gray Ranch; do not representsuc- ProfessionalPaper 134, pp.1,-70. Creek Hidalgo County, New Mexico;sec. 16, T.325., cessivetime intervals. Instead, sam- Rigby, A of Gillisonchusgillianus J K., Jr.,1981., skeleton W., NMPM; 37"30'28'N., 108"52'07'W. pling biases or facies differences have (Mammalia; Condylarthra) from the early Paleocene R. 20 Largo-meadow, in the Sangre de Cristo controlled the occurrence of certain (Puercan)Ojo Alamo Sandstone,San Juan Basin, New Valle (0.9 mammal taxa (notably Taeniolabis). Mexico, with comments on the local stratigraphy of Mountains, 1.5 km mi) northwest of Osha BetonnieTsosie Wash; in Lrcas, S. G., et al. (eds.), Passand 20.9km (13mi) east-southeastof Taos; Advances in San Juan Basin paleontology: University TaosCounty, New Mexico; sec.3, T. 24 N., R. Sinclairand Granger (1974)and, most re- of New Mexico Press,Albuquerque, New Mexico, pp. 15E., NMPM; 36"20'54'N.,105'20'25'W. cently,Lindsay and others(1981) favored the 89-126. White Place-locality, in PlayasValley 18.8km (11.7 first explanation.Matthew (1937)and, most Russell,D. E.,7957, Le Paleocenecontinental d'Amerique mi) east of Animas; Hidalgo County, New Mex- recently,Van Valen (1978)favored the second du Nord: Memoires du Museum National d'Histoire ico; 31'58'15"N., 108'36'40"W.; not: Playas. Naturelle, new series (C), v. 1,6,pp. 1-99. explanation. Wind Canyon-
August 1984 New MexicoGeology