Matthew R. Borths

Madagascar is known for its diverse and intriguing endemic fauna. The carnivorans are no exception and include eight extant endemic species comprising the family Eupleridae (Veron et al., 2017), as...

Following decades of increasing collaboration and organization, the United States natural science collections community is uniting around the creation of a national center supporting biological collections. Community consultations identified eight major themes that a center could encompass to manage, unify, and strategically expand the vast specimen/sample infrastructure and associated data stored in biological collections, address challenges facing physical biodiversity collections, and, importantly, coordinate across diverse research and education sectors. The center would foster workforce development, ethical collaboration with Indigenous communities, expand a digital infrastructure to provide broad access to collections data, and innovation in fields like artificial intelligence for data capture, management, and analysis. Ultimately, a center would provide sustainable, long-term government and private support for biodiversity science that integrates the use of biological collections to foster innovations and networks that address critical societal challenges and benefit public health, environmental conservation, and the bioeconomy.

Hyainailourine hyaenodonts are among the largest terrestrial carnivorous mammals known. The clade is widely dispersed, found in Eurasia, North America, and Afro-Arabia in the Paleogene and early Neogene. In this study, we describe dental and postcranial material from Simbakubwa kutokaafrika, gen. et sp. nov., the most complete hyainailourine known from sub-Saharan Africa. The material is from a relatively young adult from the early Miocene locality of Meswa Bridge, Kenya. Simbakubwa differs from Hyainailouros in exhibiting lingually oriented molar protocones, gracile metastyles, and buccolingually compressed, shearing canines. Like other large Miocene hyainailourines, Simbakubwa has deep carnassial notches on the molars and tall paracones fused to shorter metacones forming single piercing cusps. A Bayesian phylogenetic analysis recovers Simbakubwa as the sister taxon of a clade of large-bodied Miocene hyainailourines that includes Hyainailouros and Megistotherium. Bayesian ancestral state reconstruction supports an Afro-Arabian origin for Hyainailourinae with subsequent dispersal to Eurasia during the early Miocene. Regression analysis based on carnassial size is applied to Simbakubwa and closely related hyainailourines, recovering a body mass up to 1,500 kg for the new taxon. The evolution and extinction of Hyainailourinae offers important insights for interpreting ecological transitions from Paleogene to Neogene faunas in Afro-Arabia and Eurasia.

Prionogale breviceps is a tiny carnivorous mammal from the early Miocene of eastern Africa. Originally, specimens were interpreted as the adult morphology of the taxon. The dentition did not obviously align Prionogale with the carnivorous lineages present in Afro-Arabia during the early Miocene: Hyaenodonta and Carnivora. When Namasector was discovered in Namibia, the small taxa were placed together in Prionogalidae and aligned with Hyaenodonta. In this study, based on comparisons to hyaenodont specimens preserving deciduous dentition, the holotype of Prionogale is reinterpreted as preserving dP3 and dP4. Some of the lower dental specimens attributed to the taxon preserve dp4. The holotype of Namasector also preserves deciduous dental material. A phylogenetic analysis that includes deciduous dental characters for a broader sample of hyaenodonts resolved Prionogalidae as a clade. Understanding of the deciduous dentition of Prionogale allows future analyses to compare homologous morphology, and to explore the environmental factors that shaped carnivorous mammal evolution through the Miocene.

Throughout the Paleogene, most terrestrial carnivore niches in Afro-Arabia were occupied by Hyaenodonta, an extinct lineage of placental mammals. By the end of the Miocene, terrestrial carnivore niches had shifted to members of Carnivora, a clade with Eurasian origins. The transition from a hyaenodont-carnivore fauna to a carnivoran-carnivore fauna coincides with other ecological changes in Afro-Arabia as tectonic conditions in the African Rift System altered climatic conditions and facilitated faunal exchange with Eurasia. Fossil bearing deposits in the Nsungwe Formation in southwestern Tanzania are precisely dated to ~25.2 Ma (late Oligocene), preserving a late Paleogene Afro-Arabian fauna on the brink of environmental transition, including the earliest fossil evidence of the split between Old World monkeys and apes. Here we describe a new hyaenodont from the Nsungwe Formation, Pakakali rukwaensis gen. et sp. nov., a bobcat-sized taxon known from a portion of the maxilla that preserves a deciduous third premolar and alveoli of dP⁴ and M¹. The crown of dP³ bears an elongate parastyle and metastyle and a small, blade-like metacone. Based on alveolar morphology, the two more distal teeth successively increased in size and had relatively large protocones. Using a hyaenodont character-taxon matrix that includes deciduous dental characters, Bayesian phylogenetic methods resolve Pakakali within the clade Hyainailouroidea. A Bayesian biogeographic analysis of phylogenetic results resolve the Pakakali clade as Afro-Arabian in origin, demonstrating that this small carnivorous mammal was part of an endemic Afro-Arabian lineage that persisted into the Miocene. Notably, Pakakali is in the size range of carnivoran forms that arrived and began to diversify in the region by the early Miocene. The description of Pakakali is important for exploring hyaenodont ontogeny and potential influences of Afro-Arabian tectonic events upon mammalian evolution, providing a deep time perspective on the stability of terrestrial carnivore niches through time.

Hyaenodonta is a diverse clade of carnivorous mammals that were part of terrestrial faunas in the Paleogene of Eurasia and North America, but the oldest record for the group is Afro-Arabian, making the record there vital for understanding the evolution of this wide-spread group. Previous studies show an ancient split between two major clades of hyaenodonts that converged in hypercarnivory: Hyainailourinae and Hyaenodontinae. These clades are each supported by cranial characters. Phylogenetic analyses of hyaenodonts also support the monophyly of Teratodontinae, an Afro-Arabian clade of mesocarnivorous to hypercarnivorous hyaenodonts. Unfortunately, the cranial anatomy of teratodontines is poorly known, and aligning the clade with other lineages has been difficult. Here, a new species of the phylogenetically controversial teratodontine Masrasector is described from Locality 41 (latest Priabonian, late Eocene) from the Fayum Depression, Egypt. The hypodigm includes the most complete remains of a Paleogene teratodontine, including largely complete crania, multiple dentaries, and isolated humeri. Standard and “tip-dating” Bayesian analyses of a character-taxon matrix that samples cranial, postcranial, and dental characters support a monophyletic Masrasector within Teratodontinae, which is consistently placed as a close sister group of Hyainailouridae. The cranial morphology of Masrasector provides new support for an expanded Hyainailouroidea (Teratodontinae + Hyainailouridae), particularly characters of the nuchal crest, palate, and basicranium. A discriminant function analysis was performed using measurements of the distal humerus from a diverse sample of extant carnivorans to infer the locomotor habits of Masrasector. Masrasector was assigned to the “terrestrial” locomotor category, a result consistent with the well-defined medial trochlear ridges, and moderately developed supinator crests of the specimens. Masrasector appears to have been a fast-moving terrestrial form with a diverse diet. These specimens considerably improve our understanding of Teratodontinae, an ancient member of the Afro-Arabian mammalian fauna, and our understanding of hyaenodont diversity before the dispersal of Carnivora to the continent near the end of the Paleogene.

Deciduous dentition and dental eruption of Hyainailouroidea (Hyaenodonta, “Creodonta,” Placentalia, Mammalia)

Hyaenodonta is a diverse, extinct group of carnivorous mammals that included weasel- to rhinoceros-sized species. The oldest-known hyaenodont fossils are from the middle Paleocene of North Africa and the antiquity of the group in Afro-Arabia led to the hypothesis that it originated there and dispersed to Asia, Europe, and North America. Here we describe two new hyaenodont species based on the oldest hyaenodont cranial specimens known from Afro-Arabia. The material was collected from the latest Eocene Locality 41 (L-41, ∼34 Ma) in the Fayum Depression, Egypt.Akhnatenavus nefertiticyonsp. nov. has specialized, hypercarnivorous molars and an elongate cranial vault. InA. nefertiticyonthe tallest, piercing cusp on M¹–M²is the paracone.Brychotherium ephalmosgen. et sp. nov. has more generalized molars that retain the metacone and complex talonids. InB. ephalmosthe tallest, piercing cusp on M¹–M²is the metacone. We incorporate this new material into a series of phylogenetic analyses using a character-taxon matrix that includes novel dental, cranial, and postcranial characters, and samples extensively from the global record of the group. The phylogenetic analysis includes the first application of Bayesian methods to hyaenodont relationships.B. ephalmosis consistently placed within Teratodontinae, an Afro-Arabian clade with several generalist and hypercarnivorous forms, andAkhnatenavusis consistently recovered in Hyainailourinae as part of an Afro-Arabian radiation. The phylogenetic results suggest that hypercarnivory evolved independently three times within Hyaenodonta: in Teratodontinae, in Hyainailourinae, and in Hyaenodontinae. Teratodontines are consistently placed in a close relationship with Hyainailouridae (Hyainailourinae + Apterodontinae) to the exclusion of “proviverrines,” hyaenodontines, and several North American clades, and we propose that the superfamily Hyainailouroidea be used to describe this relationship. Using the topologies recovered from each phylogenetic method, we reconstructed the biogeographic history of Hyaenodonta using parsimony optimization (PO), likelihood optimization (LO), and Bayesian Binary Markov chain Monte Carlo (MCMC) to examine support for the Afro-Arabian origin of Hyaenodonta. Across all analyses, we found that Hyaenodonta most likely originated in Europe, rather than Afro-Arabia. The clade is estimated by tip-dating analysis to have undergone a rapid radiation in the Late Cretaceous and Paleocene; a radiation currently not documented by fossil evidence. During the Paleocene, lineages are reconstructed as dispersing to Asia, Afro-Arabia, and North America. The place of origin of Hyainailouroidea is likely Afro-Arabia according to the Bayesian topologies but it is ambiguous using parsimony. All topologies support the constituent clades–Hyainailourinae, Apterodontinae, and Teratodontinae–as Afro-Arabian and tip-dating estimates that each clade is established in Afro-Arabia by the middle Eocene.