Craniodental morphology and phylogeny of marsupials

Abstract

The current literature on marsupial phylogenetics includes numerous studies based on analyses of morphological data with relatively limited sampling of Recent and fossil taxa, and many studies based on analyses of molecular data that include a dense sampling of Recent taxa, but relatively few that combine both data types. Another dichotomy in the marsupial phylogenetic literature is between studies that focus on New World taxa, others that focus on Sahulian taxa. To date, there has been no attempt to assess the phylogenetic relationships of the global marsupial fauna, based on combined analyses of morphology and molecular sequences, for a dense sampling of Recent and fossil taxa. For this report, we compiled morphological and molecular data from an unprecedented number of Recent and fossil marsupials. Our morphological data consist of 180 craniodental characters that we scored for 97 species representing every currently recognized Recent genus, 42 additional ingroup (crown-clade marsupial) taxa represented by well-preserved fossils, and 5 outgroups (non-marsupial metatherians). Our molecular data comprise 24.5 kb of DNA sequences from whole-mitochondrial genomes and six nuclear loci (APOB, BRCA1, GHR, RAG1, RBP3 and VWF) for 97 marsupial terminals (the same Recent taxa scored for craniodental morphology) and several placental and monotreme outgroups. The results of separate and combined analyses of these data using a wide range of phylogenetic methods support many currently accepted hypotheses of ingroup (marsupial) relationships, but they also underscore the difficulty of placing fossils with key missing data (e.g., †Evolestes), and the unique difficulty of placing others that exhibit mosaics of plesiomorphic and autapomorphic traits (e.g., †Yalkaparidon). Unique contributions of our study are (1) critical discussions and illustrations of marsupial craniodental morphology, including descriptions and illustrations of some features never previously coded for phylogenetic analysis; (2) critical assessments of relative support for many suprageneric clades; (3) estimates of divergence times derived from tip-and-node dating based on uniquely taxon-dense analyses; and (4) a revised, higher-order classification of marsupials accompanied by lists of supporting craniodental synapomorphies. Far from the last word on these topics, this report lays the foundation for future research that may be enabled by the discovery of new fossil taxa, better-preserved material of previously described taxa, novel morphological characters, and improved methods of phylogenetic analysis.

Cranial remains of Ramsayia magna from the Late Pleistocene of Australia and the evolution of gigantism in wombats (Marsupialia, Vombatidae)

“…(2010), Sharp (2016), Sharp & Rich (2016), Trusler & Sharp (2016) and Beck et al . (2022). Such parietal sinuses are present in a range of extinct large‐bodied Vombatiformes, including Nimbadon , Neohelos , Silvabestius , Thylacoleo , Palorchestes , Kolopsis and Diprotodon .…”

“…This last sinus is incomplete but is the largest preserved: 42 mm in length and 50 mm in height; it probably represents the dorsal part of the posterior epitympanic sinus that is present in other vombatids and most other diprotodontians (Beck et al . 2022).…”

“…Only a single mental foramen appears to have been present, as in other vombatids (Beck et al . 2022, char. 98): it forms a deep sulcus in the mandible c .…”

Late middle Miocene Metatheria (Mammalia: Didelphimorphia and Paucituberculata) from Juan Guerra, San Martín Department, Peruvian Amazonia

“…The presence of a well-developed posterior cingulid in MUSM 4018 is a striking feature, since this structure was until recently considered to be absent in all didelphids, and also in paucituberculatans and microbiotheriids (Beck et al, 2021). A posterior cingulid is now described for two didelphids, as well as in basal ameridelphians (Beck et al, 2021) and caenolestid paucituberculatans (Abello et al, 2021).…”

“…The following characteristics allowed the assignment of this material to Didelphidae, according to Voss and Jansa (2009): tribosphenic lower molars, with a developed anterior cingulid (notched for the hypoconulid of the preceding tooth), as well as notched paracristids. However, it is important to mention that some authors consider that there are no synapomorphies on the lower molars that undoubtedly characterize the family Didelphidae (Beck et al, 2021). Compared to other Miocene didelphids, the TAR-31 specimen is much smaller than Didelphis solimoensis Cozzuol, Goin, de los Reyes, and Ranzi, 2006 from Acre (Cozzuol et al, 2006), besides having less developed anterior cingulid and more compressed entoconid.…”