Comprehensive total evidence phylogeny of chinchillids (Rodentia, Caviomorpha): Cheek teeth anatomy and evolution

Abstract

Rodents are the most diverse order of extant mammals, and caviomorph rodents, or New World hystricognaths, have a remarkable morphological disparity and a long fossil record that begins in the Eocene. Chinchilloidea is a poorly understood clade within Caviomorpha, from an evolutionary and phylogenetic perspective. It includes the extant families Chinchillidae and Dinomyidae, the extinct Neoepiblemidae and Cephalomyidae, and several extinct chinchilloids without a clear phylogenetic position, like Eoincamys, Borikenomys, Chambiramys, Ucayalimys, Incamys, Saremmys, Garridomys and Scotamys. The family Chinchillidae includes the extant Chinchilla and Lagidium, grouped in Chinchillinae, and the only living Lagostominae, Lagostomus maximus. Among extinct chinchillids, Eoviscaccia (early Oligocene-early Miocene of Argentina, Bolivia and Chile), Prolagostomus (early-middle Miocene of Argentina, Bolivia and Chile) and Pliolagostomus (early-middle Miocene of Argentina) are the only genera originally described as members of the family. Based on the study of specimens with unworn or little-worn cheek teeth, belonging to extinct and extant taxa, we propose homologies of the cheek teeth structures and perform a combined molecular and morphological phylogenetic analysis including extinct and extant taxa of all families of Chinchilloidea and all genera of Chinchillidae. Our phylogenetic analysis recovered three major lineages in the evolutionary history of Chinchilloidea. The first major lineage is composed of the extant taxa Chinchilla, Lagidium and Lagostomus, and the extinct genera Eoviscaccia, Prolagostomus, Pliolagostomus, Garridomys, Incamys, Loncolicu and Saremmys. Cephalomyid (Banderomys, Cephalomys, Litodontomys, Soriamys) and neoepiblemid (Neoepiblema, Perimys, Phoberomys, Scotamys) genera are part of the second major lineage, while dinomyids such as Dinomys, Drytomomys, Scleromys, 'Scleromys' and Tetrastylus constitute the third major lineage within Chinchilloidea. The phylogenetic position of some taxa previously considered as incertae sedis chinchilloids or without a clear suprageneric group (i.e. Incamys, Saremmys, Garridomys and Loncolicu) show that they belong to pan-Chinchillidae and conform the stem Chinchillidae along with Eoviscaccia. The euhypsodont crown Chinchillidae includes the living subfamilies Chinchillinae and Lagostominae. Dinomyidae and Eoincamys pascuali are recovered as the sisters of a major clade composed by 'Cephalomyidae'+Neopiblemidae and pan-Chinchillidae, and Chambiramys sylvaticus occupies a basal position to the same clade. Four major radiation events are identified in the evolutionary history of Chinchilloidea. The analysis of new morphological characters linked with molecular

Late middle Miocene caviomorph rodents from Tarapoto, Peruvian Amazonia

“…As noted by Walton [ 18 ], Microscleromys shows an occlusal pattern similar to Scleromys , as well as to chinchilloids in general (i.e., high-crowned teeth with a taeniodont pattern and oblique loph[-id]s, the absence of the second transverse cristid or its reduction on lower molars, and the absence of the metaloph and third transverse crest, or the reduction of the latter to notably a mesoloph on upper molars). According to the recent phylogenetic analyses of Boivin et al [ 4 ], the phylogenetic position of Microscleromys , but also those of Eoincamys , Incamys and Scleromys were retrieved as stem representatives of Chinchilloidea (but see [ 127 , 145 , 146 ]). Finally, as noted by Walton [ 18 , 37 ], Ricardomys shows an occlusal morphology similar to Adelphomys and other adelphomyine octodontoids.…”

Cavioids, Chinchilloids, and Erethizontoids (Hystricognathi, Rodentia, Mammalia) of the Early Miocene Pampa Castillo Fauna, Chile

“…We follow the dental nomenclature of Boivin and Marivaux (2020), and note differences from the terminology of Rasia et al (2021) where relevant. We use the term "hypselodont" to refer to teeth that are rootless and ever growing.…”

“…AFFINITIES: Perimys is generally considered a member of the extinct chinchilloid subgroup Neoepiblemidae; per Rasia and Candela (2018), Neoepiblemidae includes the early Miocene, medium-sized Perimys and Doryperimys Kramarz et al, 2015, and the late Miocene, gigantic rodents Phoberomys Kraglievich, 1926, andNeoepiblema Ameghino, 1889. Most phylogenetic analyses place Perimys as the earliest diverging neoepiblemid (Rasia and Candela, 2018;Busker et al, 2019;Kerber and Sanchez-Villagra, 2019;Rasia et al, 2021). However, Boivin et al (2019a), the only study to include Perimys in an analysis of all caviomorphs, recovered it as a stem cavioid.…”

“…As on p4, the metalophulid I of m1 and m2 are straight and transversely oriented. In the m1-2 of SGOPV 2703, and the m1 of SGOPV 2699, the anterofossettid is completely separated from the mesoflexid/fossettid by the neomesolophid (= metalophulid II sensu Rasia et al, 2021), but in ml-2 of SGOPV 2701 and the m2 of SGOPV 2699 the neomesolophid does not join metalophulid I, so the fossettids are merged. The anterolabial corners of ml and m2 of SGOPV 2700 are damaged, so their details are unknown.…”

“…The posteroloph is straight and extends posterolabially from the hypocone. The labial end of the posteroloph is notably thicker than where it joins the hypocone, likely reflecting that it has merged with the mesoloph (Boivin and Marivaux, 2020;Rasia et al, 2021). The protocone extends farther lingually than the hypocone.…”