Stylar Cusps Research Articles

New material of Carolocoutoia ferigoloi (Mammalia, Marsupialia, Didelphimorphia): Systematic affinities and dietary inferences

Carolocoutoia ferigoloi is one of the largest metatherians of the Itaboraí fauna (Early Eocene, Southeastern Brazil). It was originally identified from a single upper molar with a markedly bunodont crown, wrinkled enamel, and a robust protocone. Here, we describe a nearly complete right dentary of C. ferigoloi with the alveoli of the premolars and first lower molar, a very worn second lower molar, complete third and fourth lower molars, and a right second upper molar. Carolocoutoia differs from other protodidelphids in having inflated, conical trigonid cusps, a more flattened entoconid, a developed entocristid, and a supernumerary cusp labial to the entoconid. Carolocoutoia was recovered in our phylogenetic analysis as the sister taxon of Protodidelphis ), since both share the presence of an anteriorly recurved dentary, wrinkled enamel, and a sinuous crest between stylar cusps B and D. The inflated, conical trigonid cusps of Carolocoutoia represent an evolutionary convergence with other South American Paleogene mammals, such as some ungulates, and the polydolopimorphian Roberthoffstetteria. We also present the second record of a pathology (molar extrusion) in a metatherian from Itaboraí. Based on its molar crown morphology, Carolocoutoia ferigoloi was a specialized frugivorous metatherian. The occurrence of a specialized frugivorous protodidelphid in the Itaboraí fauna is in line with the well-established increase in global temperatures and the expansion of tropical forests after the Paleocene-Eocene Thermal Maximum (around 55.5–55.3 million years ago).

A probable koala from the Oligocene of central Australia provides insights into early diprotodontian evolution

Diprotodontians are the morphologically and ecologically most diverse order of marsupials. However, an approximately 30-million-year gap in the Australian terrestrial vertebrate fossil record means that the first half of diprotodontian evolution is unknown. Fossil taxa from immediately either side of this gap are therefore critical for reconstructing the early evolution of the order. Here we report the likely oldest-known koala relatives (Phascolarctidae), from the late Oligocene Pwerte Marnte Marnte Local Fauna (central Australia). These include coeval species of Madakoala and Nimiokoala, as well as a new probable koala (?Phascolarctidae). The new taxon, Lumakoala blackae gen. et sp. nov., was comparable in size to the smallest-known phascolarctids, with body-mass estimates of 2.2–2.6 kg. Its bunoselenodont upper molars retain the primitive metatherian condition of a continuous centrocrista, and distinct stylar cusps B and D which lacked occlusion with the hypoconid. This structural arrangement: (1) suggests a morphocline within Phascolarctidae from bunoselenodonty to selenodonty; and (2) better clarifies the evolutionary transitions between molar morphologies within Vombatomorphia. We hypothesize that the molar form of Lumakoala blackae approximates the ancestral condition of the suborder Vombatiformes. Furthermore, it provides a plausible link between diprotodontians and the putative polydolopimorphians Chulpasia jimthorselli and Thylacotinga bartholomaii from the early Eocene Tingamarra Local Fauna (eastern Australia), which we infer as having molar morphologies consistent with stem diprotodontians.

Urrayira whitei gen. et sp. nov.: a dasyuromorphian (Mammalia: Marsupialia) with incipient zalambdodonty from the Middle Pleistocene of Queensland, Australia

Urrayira whitei gen. et sp. nov. is described based on dental remains from middle Pleistocene cave sites at Mount Etna, Queensland. Its higher-level systematic affinities are unclear but it appears to be a dasyuromorphian. It is unusual in having a specialized reduced dentition characterized by reduction of the stylar cusps, protocone and talonid, resulting in an incipiently zalambdodont morphology that emphasizes the shearing crests. In addition, only two upper premolars are present, and we assume that it is P3 that has been suppressed, as has occurred multiple times within Dasyuridae. Maximum parsimony and undated Bayesian analyses of a 174 morphological character matrix intended to resolve relationships within Dasyuromorphia, with a molecular scaffold enforced, suggest that Urrayira is a dasyurid. In the maximum parsimony analysis, Urrayira is sister to Planigale gilesi (which also lacks P3), whereas in the undated Bayesian analysis, Urrayira resolves as part of a trichotomy at the base of Dasyuridae, together with Sminthopsinae and Dasyurinae; however, support values are generally low throughout the tree. While the majority of rainforest-adapted taxa in the Mount Etna sites became either extinct or were locally extirpated at, or soon after, 280 ka, there is no evidence that U. whitei gen. et sp. nov. even persisted until that time. Urrayira whitei was likely a rainforest-specialist, thus may have been particularly vulnerable to incipient effects of the Mid-Brunhes climatic shift towards aridity that eventually drove the disappearance of the Mount Etna rainforest and its associated fauna.Jonathan Cramb* [jonathan.cramb@qm.qld.gov.au], Queensland Museum, PO Box 3300, South Brisbane BC, Queensland 4101, Australia; Scott Hocknull [scott.hocknull@qm.qld.gov.au], Queensland Museum, PO Box 3300, South Brisbane BC, Queensland 4101, Australia; Robin M. D. Beck [r.m.d.beck@salford.ac.uk], School of Science, Engineering and Environment, University of Salford, Manchester M5 4WT, UK; Shimona Kealy [shimona.kealy@anu.edu.au], Archaeology and Natural History, College of Asia and the Pacific, The Australian National University, Canberra, ACT, 2601, Australia; Gilbert J. Price [g.price1@uq.edu.au], School of Earth and Environmental Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.

UNA NUEVA ESPECIE DE LUTREOLINA THOMAS, 1910 (MARSUPIALIA, DIDELPHIDAE) DEL PLEISTOCENO TEMPRANO DE LA PAMPA AUSTRAL (PROVINCIA DE BUENOS AIRES, ARGENTINA)

We describe Lutreolina tonnii sp. nov. (Mammalia, Metatheria, Marsupialia, Didelphimorphia, Didelphidae), recovered from Early (or Early–Middle) Pleistocene deposits of the coastal cliffs near Necochea City in Buenos Aires Province, Argentina. Its holotype, a right maxillary with M1-3, indicates that it belongs to the largest species of the genus, including extinct and extant species. It also differs from other species of the genus in having more anteroposteriorly compressed protocones in the upper molars. It differs from the living species in that the maxillary-jugal contact is less horizontal in its posterior two-thirds, has a deeper ectoflexus in M3, and has a shallow but distinct internal (lingual) crest linking the bases of stylar cusps B and D in M1-3. The new species is the fourth known up to now for the South American record, and the third for the Plio–Pleistocene of the Pampean Region, thus suggesting a considerable diversity for this genus in mid-latitudes of this continent by the end of the Cenozoic Era.

Ancestral radiation of paenungulate mammals (Paenungulatomorpha)—new evidence from the Paleocene of Morocco

ABSTRACT Reported here is the discovery of a new mammal from the middle Paleocene of the Ouled Abdoun phosphate basin, Morocco. Hadrogeneios phosphaticus, gen. et sp. nov., is described based on dental and gnathic specimens. Comparative dental anatomy and CT scan observations support stem relationships to paenungulates. The cladistic analysis relates Hadrogeneios to paenungulatomorphs, especially based on the shared morphotypic condition of a dilambdodont ectoloph linked to inflated stylar cusps. Within the Paenungulatomorpha, Hadrogeneios is plesiomorphic not only with respect to crown paenungulates, but also to Abdounodus and Ocepeia, making it the basalmost known paenungulatomorph. Hadrogeneios, on the other hand, displays a peculiarly specialized mandibular symphyseal region (mentum), which is enlarged and raised high above the cheek teeth, and bears at its apex small incisors that are innervated and vascularized by a peculiar long and thin dorsal canaliculus. This is tentatively interpreted as a plier-like dental apparatus specialized for enhanced oral gripping function of the food, with increasing grip strength or enhanced grip precision. A composite reconstruction of the lower jaw of Hadrogeneios phosphaticus, based on 3D modeling from CT scans, is provided. Hadrogeneios, Abdounodus, and Ocepeia, all from the same Ouled Abdoun Paleocene phosphate levels, are the very rare witnesses of the first evolution and diversification of the endemic African ungulates phylogenetically preceding the modern paenungulate orders.

The Gondwanan Origin of Tribosphenida (Mammalia)

A review of the Southern Hemisphere Mesozoic tribosphenic mammal fossil record supports the hypothesis that Tribosphenida arose in the Southern Hemisphere during the Early Jurassic, around 50 million years prior to the clade’s reliably dated first appearance in the Northern Hemisphere. Mesozoic Southern Hemisphere tribosphenic mammals are known from Australia, Madagascar, South America and the Indian subcontinent, and are classified into three families: Bishopidae (fam. nov.), Ausktribosphenidae and Henosferidae. These are stem therians, and considerable morphological evolution occurred within the lineage between the Jurassic and late Early Cretaceous. Important dental modifications include a graduated transition between premolars and molars, development of molar wear facets V and VI, loss of facets for postdentary bones, reduction in the Meckelian groove and development of a true dentary angle. Previous classifications of Southern Hemisphere tribosphenic mammals are ambiguous because information from the upper dentition has been lacking. Upper molars attributed to the late Early Cretaceous (Albian) Southern Hemisphere group Bishopidae fam. nov. are now known to possess a prominent protocone and stylar cusp C. We thus consider bishopids to be the sister group to Theria. Timothy F. Flannery [tim.flannery@textpublishing.com.au], Kristofer M. Helgen [Kris.Helgen@Australian.Museum], Australian Museum, 1 William St Sydney 2000, Australia; Thomas H. Rich [trich@museum.vic.gov.au], Museums Victoria, PO Box 666, Q28 Melbourne, Victoria 3001, Australia; Patricia Vickers-Rich [pat.rich@monash.edu; prich@swin.edu.au], School of Earth, Atmosphere and Environment, Monash University, Victoria 3800, Australia; Swinburne University of Science and Technology, Department of Chemistry and Biotechnology, Hawthorn, Victoria 3122, Australia; Elizabeth Grace Veatch [elizabeth.veatch@gmail.com], National Museum of Natural History, Smithsonian Institution, Washington, DC 20013, USA.

Early Late Cretaceous mammals from southern Patagonia (Santa Cruz province, Argentina)

The Upper Cretaceous (Cenomanian) Mata Amarilla Formation in western central Santa Cruz province of Argentina has yielded fragmentary teeth of a large ?docodontan, an australosphenidan, a meridiolestidan (Amarillodon meridionalis gen. et sp. nov.), and a stem dryolestid (Treslagosodon shehuensis gen. et sp. nov.). These represent the first possible records for docodontans, Cretaceous australosphenidans, and stem dryolestids in South America. Both ?docodontan tooth fragments are unusually large and exhibit potential durophagous adaptation. The Amarillodon gen. nov. lower (?deciduous) posterior premolar has a trigonid angulation of 100° and is autapomorphic by a large and exoedaenodont distolabial accessory cusp on the distal cingulid. Both the mesial and distal cingulid are shelf-like. The mesiolabial upper molar fragment of the ausktribosphenid australosphenidan is similar to an upper M1 of aff. ?Bishops from the lower Albian (Lower Cretaceous) of Australia by its large stylar cusp ?C and breached paracone. The lower molar of the new stem dryolestid is characterized by a large talonid cusp d and a mesio-distally strongly compressed mesial root that is weaker than the distal one. The australosphenidan, if corroborated, suggests faunal interrelationships between Australia and South America by the late Early/early Late Cretaceous.

Cranial anatomy of Andinodelphys cochabambensis, a stem metatherian from the early Palaeocene of Bolivia

Andinodelphys cochabambensis Marshall & Muizon, 1988 is one of the best preserved metatherian species from the early Palaeocene fauna of Tiupampa (Bolivia). It is represented by five almost complete skulls, three of them being securely associated to sub-complete to partial skeleton. Four skulls could be extracted from a block including several intermingled skeletons. The present paper provides a thorough description of the dental, cranial, and dentary anatomy of A. cochabambensis. The cranial anatomy of A. cochabambensis is similar to that of Pucadelphys andinus. The skull of Andinodelphys however differs from that of Pucadelphys in its larger size and proportionally longer rostrum. Other differences include the presence, in Andinodelphys, of large anteriorly protruding I1s, small palatal vacuities, a transverse canal, and a small hypotympanic sinus. Andinodelphys has the same dental formula as Pucadelphys (I 5/4, C 1/1, P 3/3, M4/4), the plesiomorphic condition for metatherians. Furthermore, both genera share the lack a tympanic process of the alisphenoid, a deep groove for the internal carotid artery at the anterior apex of the promontorium, a small prootic canal perforating the lateral edge of the petrosal and opening laterally in the deep sulcus for the prootic sinus, and a vestigial anterior lamina of the petrosal. Dentally Andinodelphys closely resembles Pucadelphys, the two genera differing in the larger size of the former and in the inconstant presence in the former of a twinned stylar cusp C. Although 25% smaller, the cheek teeth of Andinodelphys closely resemble those of Itaboraidelphys camposi from the early Eocene of Itaboraí (Brazil). As far as dental morphology is concerned, both genera are likely to have diverged from a direct common ancestor, probably Andinodelphys-like, with Itaboraidelphys displaying more derived dental structures. Two isolated petrosal from Itaboraí (Type 2 petrosals) are morphologically close to those of Andinodelphys but distinctly larger. In this paper, a previous interpretation including the teeth of Itaboraidelphys and these petrosals in the same taxon is followed. A phylogenetic analysis retrieved Itaboraidelphys as a sister taxon of the clade Pucadelphys + Andinodelphys, thus lending support to inclusion of the former in the Pucadelphyidae. Three sets of parsimony analyses were performed. A first set of analyses (with all characters) retrieved a strict consensus tree with a clade as follows: (pucadelphyids, (deltatheroidans (stagodontids, Gurlin Tsav skull-GTS), sparassodonts)). An implied weighting analysis with the same data matrix placed the stagodontids in an early diverging position but retained a clade (pucadelphyids, (deltatheroidans, (GTS, sparassodonts))), the deltatheroidans, being therefore inserted in the pucadelphydans. This result implies an independent arrival of pucadelphyids and sparassodonts to South America, which consequently must have been present in North America in the Late Cretaceous. Possible North American sparassodonts could be the poorly known genera Atokatheridium and Olklatheridium (currently referred to deltatheroidans) and the pucadelphyids may have been present in the Late Cretaceous of North America with the genus Aenigmadelphys. However, this hypothesis is less parsimonious (with regard to palaeobiogeography) than a single southward migration of an ancestral Pucadelphyda (Pucadelphyidae + Sparassodonta). Because the result of this first set of analyses may have been induced by heavily homoplastic dental characters related to hypercarnivory, a second set of analyses was performed excluding all the dental characters. The strict consensus is poorly resolved but retains monophyletic Marsupialia and Sparassodonta. An implied weighting analysis retrieved a monophyletic Pucadelphyda but split the deltatheroidans, the polyphyly of which is regarded as a possible artefact related to the lack of dental characters. The GTS is sister taxon to Pucadelphyda. Because the polyphyly of deltatheroidans contradicts all previous hypotheses, a third set of analyses has been performed excluding only those molar characters that supported the close relationships of the hypercarnivorous clades (deltatheroids, stagodontids, and sparassodonts). The strict consensus tree retrieved monophyletic deltatheroidans, Marsupialia and sparassodonts. An implied weighting analysis resulted in deltatheroidans forming a paraphyletic stem assemblage of Metatheria and monophyletic Pucadelphyda. The GTS was no longer related to sparassodonts but was the sister taxon of a clade including the North American taxa of the data matrix, Asiatherium, and Marsupialia. This topology, which is favoured here, supports (as well as that of the second set of analyses) a single pucadelphydan southward migration, probably in the Late Cretaceous, with a Tiupampian radiation of South American carnivorous metatherians.

Biochron and Diversity of Archaeopithecidae (Mammalia, Notoungulata) and a New Genus and Species from the Eocene of Patagonia, Argentina

Fil: Lopez, Guillermo Marcos. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Division Paleontologia Vertebrados; Argentina

Northernmost record of the Metatheria: a new Late Cretaceous pediomyid from the North Slope of Alaska

The northernmost record of Metatheria, Unnuakomys hutchisoni gen. et sp. nov., is described from the Pediomys Point locality in Upper Cretaceous (lower Maastrichtian) strata of the Prince Creek Formation cropping out along the Colville River on the North Slope of Alaska, USA (70°N). Based on over 60 specimens (including tooth-bearing dentaries and a maxillary fragment), the new taxon is unusual in having two well-developed stylar cusps in the C position flanking the deepest part of the ectoflexus. To examine the relationship between U. hutchisoni and other metatherians, U. hutchisoni was scored into the taxon character matrix of other studies. Our results corroborate prior studies that suggest the new Alaskan pediomyid. However, in contrast to other studies, we do not recover a sister-group relationship between U. hutchisoni and Pediomys elegans. Rather, our study suggests that U. hutchisoni is more closely allied with Aquilan species Iqualadelphis lactea and ?Aquiladelphis laurae. Teeth of U. hutchisoni greatly outnumber those recovered from other mammals at Pediomys Point, like Late Cretaceous localities in the Western Interior where metatherians are among the most abundant mammalian fossils. However, what differs between Late Cretaceous mid-latitude localities and the assemblage from the North Slope of Alaska is metatherian richness. Whereas other studies have reported up to a dozen species of metatherians from Late Cretaceous mid-latitude North American assemblages, to date all the metatherian teeth collected from Pediomys Point appear to belong to just U. hutchisoni. A sampling bias may play a role in this pattern. This can be tested through additional collection from the Prince Creek Formation. However, the abundance of U. hutchisoni at Pediomys Point implies that this tiny metatherian thrived in an environment well above the Arctic Circle whose climatic extremes may have acted as a biogeographical filter to other metatherians. As the first mammal to be described from the Prince Creek Formation, U. hutchisoni provides support for the existence of a northern high-latitude early Maastrichtian faunal province identified by others on the basis of its distinctive dinosaurian fauna – the Paaŋaqtat Province.http://zoobank.org/urn:lsid:zoobank.org:pub:0EF38E01-2FF4-4698-A3AD-97CF2EE6847A

Austropediomys marshalli gen. et sp. nov., a new Pediomyoidea (Mammalia, Metatheria) from the Paleogene of Brazil: paleobiogeographic implications

The Pediomyiodea has been largely regarded as a Late Cretaceous North American metatherian lineage; however, some studies have suggested that a few South American taxa could be related to this family. Herein, Austropediomys marshalli gen. et sp. nov. from the Itaborai Basin, Brazil (lower Eocene – Itaboraian SALMA), is described. Austropediomys gen. nov. represents the first report of a pediomyoid metatherian in the Paleogene of South America backed by a phylogenetic analysis. Several derived features in the upper molars support its belonging to the Pediomyoidea: presence of accessory ‘conular-like’ structures (here named conuloids) lingual to the conules; supernumerary stylar cusps; asymmetric stylar shelf, with parastylar shelf reduced to a narrow rim in M1; straight centrocrista; short and obliquely oriented prepacrista, which contacts StA in M2–3. The presence of ‘conular-like’ structures lingual to the paraconule and metaconule is identified in Austropediomys gen. nov. and in Late Cretaceous pediomyoids as well, and results in the phylogenetic analysis as a synapomorphy of the Pediomyoidea. Austropediomys gen. nov. is autapomorphyc in the presence of enlarged conuloids on protocristae. The record of a pediomyoid in the Paleogene of South America increases the temporal and biogeographical range of this lineage. Also, our results support the hypothesis that several non-related metatherian lineages dispersed from North to South America via the Caribbean Plate, most probably during the latest Cretaceous, in an island-hopping or sweepstakes model.

New material of the marsupial (Mammalia, Metatheria)Herpetotherium merriami(Stock and Furlong, ) from the John Day Formation, late Oligocene, Oregon, USA

AbstractRecently discovered specimens of the marsupialHerpetotherium merriami(Stock and Furlong, 1922) from the John Day Formation, Oregon, are described. The species was previously known only from a single (type) specimen. These additional specimens have allowed for a revised diagnosis of the species based on the presence of an additional stylar cusp on the upper molars, as well as the relative size of the stylar cusps. This new material also allows for an examination of the variability within the species and establishes a time range for the species, which extends through most of the Arikareean (late Oligocene: Ar1–Ar3: late Rupelian-Aquitanian).Herpetotherium merriamiis distinct within the genus because it is among the larger of the species, but one of the latest occurring, whereas the general pattern of the genus is a reduction in size through time.

A new family of bizarre durophagous carnivorous marsupials from Miocene deposits in the Riversleigh World Heritage Area, northwestern Queensland.

A new specimen of the bizarrely specialised Malleodectes mirabilis from middle Miocene deposits in the Riversleigh World Heritage Area provides the first and only information about the molar dentition of this strange group of extinct marsupials. Apart from striking autapomorphies such as the enormous P3, other dental features such as stylar cusp D being larger than B suggest it belongs in the Order Dasyuromorphia. Phylogenetic analysis of 62 craniodental characters places Malleodectes within Dasyuromorphia albeit with weak support and without indication of specific relationships to any of the three established families (Dasyuridae, Myrmecobiidae and Thylacinidae). Accordingly we have allocated Malleodectes to the new family, Malleodectidae. Some features suggest potential links to previously named dasyuromorphians from Riversleigh (e.g., Ganbulanyi) but these are too poorly known to test this possibility. Although the original interpretation of a steeply declining molar row in Malleodectes can be rejected, it continues to seem likely that malleodectids specialised on snails but probably also consumed a wider range of prey items including small vertebrates. Whatever their actual diet, malleodectids appear to have filled a niche in Australia’s rainforests that has not been occupied by any other mammal group anywhere in the world from the Miocene onwards.

A late-surviving apatemyid (Mammalia: Apatotheria) from the latest Oligocene of Florida, USA.

A new species of Apatemyidae, Sinclairella simplicidens, is based on four isolated teeth that were screenwashed from fissure fillings at the late Oligocene Buda locality, Alachua County, Florida. Compared to its only congener Sinclairella dakotensis, the new species is characterized by upper molars with more simplified crowns, with the near absence of labial shelves and stylar cusps except for a strong parastyle on M1, loss of paracrista and paraconule on M2 (paraconule retained but weak on M1), lack of anterior cingulum on M1–M3, straighter centrocristae, smaller hypocone on M1 and M2, larger hypocone on M3, distal edge of M2 continuous from hypocone to postmetacrista supporting a large posterior basin, and with different tooth proportions in which M2 is the smallest rather than the largest molar in the toothrow. The relatively rare and poorly-known family Apatemyidae has a long temporal range in North America from the late Paleocene (early Tiffanian) to early Oligocene (early Arikareean). The new species from Florida significantly extends this temporal range by roughly 5 Ma to the end of the Paleogene near the Oligocene-Miocene boundary (from early Arikareean, Ar1, to late Arikareean, Ar3), and greatly extends the geographic range of the family into eastern North America some 10° of latitude farther south and 20° of longitude farther east (about 2,200 km farther southeast) than previously known. This late occurrence probably represents a retreat of this subtropically adapted family into the Gulf Coastal Plain subtropical province at the end of the Paleogene and perhaps the end of the apatemyid lineage in North America.

Ganguroo robustiter, sp. nov. (Macropodoidea, Marsupialia), a middle to early late Miocene basal macropodid from Riversleigh World Heritage Area, Australia

ABSTRACT——Cranial and dental remains of the middle to early late Miocene macropodid kangaroo, Ganguroo robustiter, sp. nov., are described. Postcranial remains of G. robustiter were previously described as referable to G. bilamina. Ganguroo robustiter is more robust (approximately 20% larger) and more derived than G. bilamina and G. bites, in having a larger m4, a well-developed posterolingual ridge and lingual cingulum on P3, a longer P3/p3, and no stylar cusp C on M3–M4. We used previously published data matrices to analyze the phylogenetic relationship of G. robustiter. Both phylogenetic analyses, using craniodental and postcranial characters, place G. robustiter within Macropodidae, as the sister taxon to sthenurines and macropodines. Species of Ganguroo are not found to be monophyletic despite their extreme similarity in character scores. This may be due to the large amount of missing data for G. bilamina and G. bites for which no postcranial remains have been identified. Phylogenetic results are ambiguous, recovering unresolved trees with low bootstrap values, but the generic assignment of these taxa is maintained because they are remarkably similar. Species of Ganguroo may represent a phyletic lineage, with species increasing in size and losing cusp/cuspids on their premolars through time, which appears to coincide with a broader record of changing vegetation and climates through the middle Miocene.http://zoobank.org/urn:lsid:zoobank.org:pub:D0B542BE-C673-4260-8381-8B163A35AC36SUPPLEMENTAL DATA——Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Earliest modern bandicoot and bilby (Marsupialia, Peramelidae and Thylacomyidae) from the Miocene of the Riversleigh World Heritage Area, northwestern Queensland, Australia

ABSTRACT Recent molecular phylogenies of peramelemorphians suggest that thylacomyids (bilbies) and peramelids (modern bandicoots) diversified sometime in the late Oligocene or early Miocene. Until now, however, the earliest fossil evidence of thylacomyids and peramelids was from the Australian Pliocene. Here we describe the oldest peramelid and thylacomyid from the middle Miocene of the Riversleigh World Heritage Area, northwestern Queensland. The peramelid, Crash bandicoot, gen. et sp. nov., is represented by a single maxilla containing M1–3 that exhibits peramelid synapomorphies, including development of a metaconular hypocone, an incomplete centrocrista, and well-developed anterior cingulum. The thylacomyid, Liyamayi dayi, gen. et sp. nov., is represented by M2 and m1, which show thylacomyid synapomorphies including a conical entoconid, a conical stylar cusp B (StB) and StD, and reduced distance between the metastyle and StD. The results of our phylogenetic analysis indicate that both species are part of crown-group Peramelemorphia. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Variation and taxonomy of Asiamerican eutherian mammalParanyctoides

A parsimony analysis of the distribution of 408 characters in 73 taxa of Cretaceous eutherians and related taxa places three species of Paranyctoides, the Asiatic P. quadrans and the North American P. sternbergi and P. maleficus, into a monophyletic taxon supported by three unambiguous synapomorphies. In this analysis P. quadrans has three autapomorphies, but in the analysis using combined terminal taxon for the entire sample of North American Paranyctoides two of these autapomorphies (development of stylar cusps C and D on upper molars) disappeared because these characters are also variably present in the North American sample. The remaining autapomorphy of P. quadrans, m3 shorter than m2, is known from a single specimen and also may be affected by individual variation. The North American sample of Paranyctoides cannot be clearly separated into distinct species on morphological or morphometric grounds and is considered as representing a single species, P. sternbergi Fox, 1979 (= P. maleficus Fox, 1984, syn. nov.). It differs from the Asiatic P. quadrans (Nesov, 1993) only in having a sharp lingual ridge on p5 and m3 longer than m2. Paranyctoides is the sister taxon to Zhelestidae; this clade is supported by four unambiguous synapomorphies.

A peculiar faunivorous metatherian from the early Eocene of Australia

I describe Archaeonothos henkgodthelpi gen. et. sp. nov., a small (estimated body mass ∼40–80 g) tribosphenic metatherian from the early Eocene Tingamarra Fauna of southeastern Queensland, Australia. This taxon, known only from a single isolated upper molar (M2 or M3) is characterised by a very distinctive combination of dental features that, collectively, probably represent faunivorous adaptations. These include: a straight, elevated centrocrista; a metacone considerably taller than the paracone; a wide stylar shelf (∼50% of the total labiolingual width of the tooth); reduced stylar cusps; a long postmetacrista; a small and anteroposteriorly narrow protocone; an unbasined trigon; and the absence of conules. Some of these features are seen in dasyuromorphians, but detailed comparisons reveal key differences between A. henkgodthelpi and all known members of this clade. A. henkgodthelpi also predates recent molecular estimates for the divergence of crown-group Dasyuromorphia. Similar dental features are see...

A new hyladelphine marsupial (Didelphimorphia, Didelphidae) from cave deposits of northern Brazil

Based on very small upper and lower molars recovered from the Quaternary limestone caves in the State of Tocantins, northern Brazil, we describe a new genus and species of a didelphimorphian marsupial. A phylogenetic analysis based on morphological + karyotypic data set recovered the new genus and species as the sister taxon to the living didelphid, Hyladelphys kalinowskii Voss, Lunde & Simons. The new taxon differs from the latter in having a slightly larger size, more inflated and blunt cusps, greater reduction in number and size of the stylar cusps, in the absence of an anterior cingulum, a deeper ectoflexus in M2, paracone and metacone subequal in M2, and narrower and eccentric protocones. The new marsupial probably weighed no more than 40 g and its molar morphology is suggestive of mixed, insectivorous-frugivorous feeding habits. Although we regard the fauna of Gruta dos Mouras cave as Pleistocene, we do not negate the possibility that a temporal mixing (“time-averaging”) of Pleistocene and Holocene specimens existed and that the newly described taxon is a living marsupial in the study area.

Invictokoala monticola gen. et sp. nov. (Phascolarctidae, Marsupialia), a Pleistocene plesiomorphic koala holdover from Oligocene ancestors

Koalas (Phascolarctidae) are uncommon elements within the Australian fossil record. The earliest representatives are recorded from late Oligocene rainforest assemblages of central Australia. In contrast, the extant Koala Phascolarctos cinereus Blainville, 1816 (the only surviving member of a once diverse family) is found only in eastern Australian open woodlands. Extinction of koalas from rainforests was previously thought to have occurred after the middle Miocene. Recent systematic cave excavations at Mt. Etna, central eastern Queensland, Australia, have revealed several remarkable new middle Pleistocene vertebrate assemblages that are dominated by rainforest-adapted taxa. Within one of the deposits, we have identified a new, but archaic, genus and species of koala. Invictokoala monticola gen. et sp. nov. shares affinities with the most plesiomorphic member of the family, Madakoala Woodburne et al., 1987 (late Oligocene), but is distinguished by possessing higher-crowned upper molars, with a tricsupate (rather than linear) paraconule on M2 (autapomorphic condition within koalas), closely positioned stylar cusps, and better-developed posterior cingulae. Thus, not only does I. monticola represent a ‘holdover’ from an Oligocene ancestor, but the Madakoala–Invictokoala stem represents a ‘ghost’ lineage within the Phascolarctidae, with no representatives known between the late Oligocene and middle Pleistocene. Previously, it was thought that the post-middle Miocene loss of koalas from rainforests may have been a result of a co-evolved dependence of koalas to open eucalypt woodlands, and/or competitive exclusion with koala-like rainforest-adapted ringtail possums. However, the inferred diet of middle Pleistocene I. monticola (i.e. non-Eucalyptus) and coeval occurrence with numerous rainforest-adapted ringtail possums does not support that hypothesis. It appears more likely that koalas had always been closely associated with rainforests, at least until the late Quaternary extinction of I. monticola. Generally, the paucity of rainforest faunal assemblages, and specifically, records of fossil koalas through the late Cenozoic drastically limits our understanding of their evolution.