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Permophiles Issue #38 200124nated by shelfal carbonates (as opposed to slope and basinal siltstonesand mudstones). Both <strong>the</strong> high-bladed M. zsuzsannae andlow-bladed M. idahoensis are from <strong>the</strong> same facies and do notindicate a difference in water mass (temperature) or province. Figure1.10 is from <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> range in species from WestTexas, as is Figure 1.11, <strong>the</strong> holotype from <strong>the</strong> Meade Peak PhosphaticShale.Mesogondolella gracilis (figs. 1.12-13) is from lower part <strong>of</strong><strong>the</strong> Meade Peak Phosphatic Shale, being most abundant in <strong>the</strong>false cap (for details <strong>of</strong> <strong>the</strong> local mining terms <strong>of</strong> <strong>the</strong> Phosphoriarefer to Behnken et al., 1986). M. gracilis is characterized by adominating high, large terminal cusp <strong>of</strong> circular outline and conicalshape, <strong>the</strong> posterior most denticles are miniscule, and in large specimensonly faintly recognizable, <strong>the</strong> platform is narrow and laterallyupturned, <strong>the</strong> blade is only partially fused, and <strong>the</strong> denticles arecommonly mostly discrete. The serrated gondolellid that co-occurswith M. gracilis is commonly identified as Jinogondolellanankingensis which has a much broader platform, a completelydifferent denticulation pattern <strong>of</strong> a lower cusp and prominent posteriordenticles and clearly represents <strong>the</strong> marker species <strong>of</strong> <strong>the</strong>Roadian at <strong>the</strong> nor<strong>the</strong>rn end <strong>of</strong> its geographic cline. Therefore, M.gracilis is Roadian. Its first appearance coincides with that <strong>of</strong> J.nankingensis.Mesogondolella gracilis (transitional to M. phosphoriensis)(fig. 1.14) occurs in <strong>the</strong> middle silt <strong>of</strong> <strong>the</strong> Meade Peak PhosphaticShale and is characterized by a large cusp that is longitudinallyelongate, small, but clearly developed posterior denticles that arefused in large specimens, and a blunt posterior platform margintermination.Mesogondolella phosphoriensis (figs. 1.15-17) occurs in <strong>the</strong>upper part <strong>of</strong> <strong>the</strong> Meade Peak Phosphatic shale, with its first appearancein <strong>the</strong> buckshot phosphorite, and it is very abundant in<strong>the</strong> rich seam. It co-occurs with J. nankingensis and a form Ibelieve to be <strong>the</strong> predecessor to “M.” bitteri that appears to bederived from J. nankingensis as it has <strong>the</strong> same denticulation pattern.I illustrate a representative specimen (fig. 1.16), a gerontic,pathologic specimen (fig. 1.15) from <strong>the</strong> rich seam and <strong>the</strong> holotype(fig. 1.17) from <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Meade Peak in ParisCanyon, just a few miles southwest <strong>of</strong> Montpelier on <strong>the</strong> northwestside <strong>of</strong> Bear Lake. M. phosphoriensis is characterized by abluntly rounded to square posterior margin, a generally triangularshape, a prominent longitudinally elongate cusp, prominent carinaldenticles that increase in size anteriorly and are discrete to partiallyfused with low short partially fused denticles on <strong>the</strong> blade,and indistinct furrows. M. gracilis, <strong>the</strong> transitional morphotype,and M. phosphoriensis all have indistinct furrows; whereas, M.prolongata and M. retortensis (n. sp.) have narrow, but distinctfurrows.Mesogondolella prolongata (fig. 1.18) occurs in <strong>the</strong> lowerpart <strong>of</strong> <strong>the</strong> Retort Phosphatic Shale where it co-occurs with M.retortensis. It is characterized by a large, slightly longitudinallyelongate cusp, delicate discrete denticles that steadily increase insize anteriorly, short only partially fused denticles on <strong>the</strong> blade,and a narrow platform. It is most like M. gracilis but differs indiscrete, closely spaced posterior denticles, a less prominent cuspand a platform that is posteriorly rounded and extends fur<strong>the</strong>r posteriorlyaround <strong>the</strong> cusp so that in large specimens a thin brim isdeveloped and in lateral pr<strong>of</strong>ile <strong>the</strong>re is commonly a bulge where<strong>the</strong> brim will develop that is not present in M. gracilis. Intermediatespecimens between <strong>the</strong> stratigraphic interval where M. gracilisis common and M. prolongata is present are not known at <strong>the</strong>present time.Mesogondolella retortensis (n.sp., fig. 1.19) occurs in <strong>the</strong>Retort Phosphatic Shale in Montana and Wyoming and <strong>the</strong> upperpart <strong>of</strong> <strong>the</strong> Gerster Limestone in <strong>the</strong> Leach Mountains, Nevada. AtDalys Spur, Montana, where it occurs in great abundance, it cooccurswith rare specimens <strong>of</strong> “M.” bitteri and Jinogonodolellaaserrata. “M.” bitteri is abundant in more shelfal deposits <strong>of</strong> <strong>the</strong>Retort in Wyoming and is common in <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> GersterLimestone through most <strong>of</strong> its extent in Nevada and Utah. M.retortensis is Wordian. It is characterized by a broad platform thatis widest near <strong>the</strong> posterior and gently narrows anteriorly, a squareto bluntly rounded posterior platform and <strong>the</strong> platform is triangularin overall outline, a prominent longitudinally elongate cusp, abrim in moderate to large specimens, <strong>the</strong> first four denticles in front<strong>of</strong> <strong>the</strong> cusp are small, <strong>of</strong> variable spacing and size distribution, <strong>the</strong>remaining carinal denticles increase in size anteriorly, <strong>the</strong> blade islow, generally short and fused, and <strong>the</strong> fusion <strong>of</strong> carinal denticlesis variable, commonly more fused on larger specimens. This formdiffers from M. rosenkrantzi from Greenland in having a fusedblade (where <strong>the</strong> Greenland forms have much more discrete anteriordenticles) and more consistent bluntly rounded posterior margin.ReferencesBehnken, F. H, Wardlaw, B. R., and Stout, L. N., 1986, Conodontbiostratigraphy <strong>of</strong> <strong>the</strong> Permian Meade Peak PhosphaticShale Member, Phosphoria Formation, sou<strong>the</strong>astern Idaho:Contributions to Geology, University <strong>of</strong> Wyoming, v. 24, no.2, p. 169-187.Orchard, M. J., and Rieber, Hans, 1998, Multielement Neogondolella(Conodonta, upper Permian – middle Triassic): Bollettino dellaSocieta Paleontologica Italiana, v. 37, no. 2-3, p. 475-488.A Global Hiatus in <strong>the</strong> Middle Permian TetrapodFossil RecordSpencer G. LucasNew Mexico Museum <strong>of</strong> Natural History1801 Mountain Road N. W.,Albuquerque,New Mexico 87104 USAFossils <strong>of</strong> tetrapods (amphibians and reptiles) have long beenused to correlate regionally Permian nonmarine strata (Lucas, 1998).However, <strong>the</strong> development <strong>of</strong> a global Permian tetrapod biostratigraphyand biochronology has been hampered by several problems.The most serious may be <strong>the</strong> presence <strong>of</strong> a global gap (hiatus)in part <strong>of</strong> <strong>the</strong> Middle Permian record <strong>of</strong> tetrapods.It has long been known that <strong>the</strong> global fossil record <strong>of</strong> Permiantetrapods has a great geographic discontinuity. Early Permian tetrapodbody fossils are known primarily from western North America(Texas, Oklahoma and New Mexico, USA) and Western Europe(principally Germany and <strong>the</strong> Czech Republic), whereas Middle-Late Permian tetrapods are known primarily from South Africa andRussia. Thus, <strong>the</strong>re is a pronounced geographic shift in <strong>the</strong> record
Permophiles Issue #38 2001FIGURE 1. Correlation <strong>of</strong> youngest North American and oldest Russian Permian tetrapod assemblages.from <strong>the</strong> youngest Early Permian and earliest Middle Permian tetrapodassemblages in Texas-Oklahoma, USA to <strong>the</strong> oldest MiddlePermian tetrapod assemblages in Russia and South Africa. Thisshift is accentuated by <strong>the</strong> fact that <strong>the</strong> oldest Permian tetrapodassemblages in South Africa and Russia are dominated by <strong>the</strong>rapsids,so <strong>the</strong>y differ significantly from <strong>the</strong> older, pelycosaur-dominatedassemblages <strong>of</strong> <strong>the</strong> American Permian. Note also that <strong>the</strong>oldest South African Permian tetrapods (Eodicynodon AssemblageZone <strong>of</strong> Rubidge, 1995) are nearly impossible to correlate to <strong>the</strong>Permian marine timescale. They are about <strong>the</strong> same age as <strong>the</strong> oldestRussian <strong>the</strong>rapsid-dominated assemblages, or perhaps slightlyolder (Rubidge and Hopson, 1990, 1996). Also, <strong>the</strong> youngest non-Russian European Permian tetrapods are from <strong>the</strong> upper Rotliegendand thus much older in <strong>the</strong> Early Permian than <strong>the</strong> youngest AmericanPermian tetrapods (Lucas, 1998). Therefore, from a practicalpoint <strong>of</strong> view, a complete record <strong>of</strong> Permian tetrapods is one thatbridges <strong>the</strong> North American Early-Middle Permian and <strong>the</strong> RussianMiddle-Late Permian records (Fig. 1).The stratigraphically highest (and youngest) tetrapod assemblagesin <strong>the</strong> American Permian are from <strong>the</strong> San Angelo, Flowerpotand Chickasha formations <strong>of</strong> Texas-Oklahoma. Olson andBeerbower (1953) identified <strong>the</strong>rapsids in <strong>the</strong> San Angelo Formation,so Olson (e.g., 1962; also see Yefremov, 1956 and Olson andChudinov, 1992) consistently correlated <strong>the</strong> tetrapod assemblage<strong>of</strong> <strong>the</strong> San Angelo and (equivalent) Flowerpot formations with <strong>the</strong>oldest Russian <strong>the</strong>rapsid-dominated assemblages (Zones I and II<strong>of</strong> Yefremov, 1937, or Titanophoneus “Superzone” <strong>of</strong> Ivakhnenkoet al., 1997). This correlation was not based on shared low-leveltaxa (genera and species), but on <strong>the</strong> supposed presence <strong>of</strong> <strong>the</strong>rapsidsin <strong>the</strong> Texas assemblage and <strong>the</strong> presence <strong>of</strong> “counterparts”25(equivalent evolutionary grade) among <strong>the</strong> Texan and Russianamphibians and caseid pelycosaurs. Recognition that <strong>the</strong> SanAngelo “<strong>the</strong>rapsid” fossils are actually pelycosaurs (e.g., Sidorand Hopson, 1995) undermines this correlation, and suggests that<strong>the</strong> <strong>the</strong>rapsid-dominated faunas, that are <strong>the</strong> oldest Permian assemblagesin Russia (and South Africa), postdate <strong>the</strong> youngestNorth American Permian faunas.Recent work on <strong>the</strong> Chickasha Formation assemblage in Oklahomahas identified <strong>the</strong> “parareptile” Macroleter, a characteristicmember <strong>of</strong> <strong>the</strong> Russian Zone I assemblage (Reisz and Laurin, 2001).Olson (1980) originally published this specimen as Seymouriaagilis and it is from Blaine County, Oklahoma in strata <strong>of</strong> <strong>the</strong>Chickasha Formation laterally equivalent to <strong>the</strong> Flowerpot Formation.Lozovsky (2001) has recently concluded that <strong>the</strong> presence <strong>of</strong>Macroleter in <strong>the</strong> Chickasha Formation, and some evolutionarygradesimilarities <strong>of</strong> Russian and Chickasha caseids, support correlation<strong>of</strong> <strong>the</strong> Chickasha to <strong>the</strong> oldest Russian <strong>the</strong>rapsid-dominatedassemblages (also see Reisz and Laurin, 2001).However, <strong>the</strong> minimum age <strong>of</strong> <strong>the</strong> tetrapod assemblages <strong>of</strong> <strong>the</strong>San Angelo, Flowerpot and Chickasha formations is constrainedby <strong>the</strong> age <strong>of</strong> <strong>the</strong> overlying Blaine Formation, which has yieldedspecies <strong>of</strong> ammonoids (Perrinites) and fusulinids (Parafusulina)that, at <strong>the</strong>ir youngest, are Roadian in age (Plummer and Scott,1937; Dunbar et al., 1960; Jones, 1971; Tharalson, 1984; DiMicheleet al., 2001). Some even consider <strong>the</strong>se fossils from <strong>the</strong> BlaineFormation to be late Leonardian (Kungurian) in age, though <strong>the</strong>San Angelo Formation has an unconformable base generally correlatedto <strong>the</strong> sequence boundary at <strong>the</strong> base <strong>of</strong> <strong>the</strong> marineGuadalupian (e.g., Ross, 1987). The Blaine Formation overlies <strong>the</strong>San Angelo and Flowerpot formations and ei<strong>the</strong>r overlies or is
Page 1 and 2: PermophilesInternational Commission
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Page 9: Some Problems and New Achievements
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