Unexpected evolutionary patterns of dental ontogenetic traits in cetartiodactyl mammals

Abstract

Studying ontogeny in both extant and extinct species can unravel the mechanisms underlying mammal diversification and specialization. Among mammalian clades, Cetartiodactyla encompass species with a wide range of adaptations, and ontogenetic evidence could clarify longstanding debates on the origins of modern specialized families. Here, we study the evolution of dental eruption patterns in early diverging cetartiodactyls to assess the ecological and biological significance of this character and shed new light on phylogenetic issues. After investigation of the ontogenetic dental series of 63 extinct genera, our parsimony reconstructions of eruption state evolution suggest that the eruption of molars before permanent premolars represents a plesiomorphic condition within Cetartiodactyla. This result substantially differs from a previous study based on modern species only. As a result, the presence of this pattern in most ruminants might represent an ancestral condition contributing to their specialized herbivory, rather than an original adaptation. In contrast, the late eruption of molars in hippopotamoids is more likely related to biological aspects, such as increases in body mass and slower pace of life. Our study mainly shows that eruption sequences reliably characterize higher level cetartiodactyl taxa and could represent a new source of phylogenetic characters, especially to disentangle the origin of hippopotamoids and cetaceans.

Characters from the deciduous dentition and its interest for phylogenetic reconstruction in Hippopotamoidea (Cetartiodactyla: Mammalia)

“…Contrary to previous studies (Orliac et al, 2010;Lihoreau et al 2015;Boisserie et al 2017a) and the present maximum-likelihood analysis, Choeropotamus no longer appears as the sister taxon of hippopotamoids, despite their common derived state for dental eruption pattern (183 2 ; Gomes Rodrigues et al 2019). Both species of Choeropotamus are sister group of the clade of Paleogene cetartiodactyls including ruminants in the parsimony analysis.…”

“…The final dataset consists of 70 taxa, including 40 hippopotamoids, and we collected data for DPs for 51 out of these 70 taxa (including 29 hippopotamoids; Table 1). The dental eruption pattern of cetartiodactyls has recently been studied and demonstrated as having a strong phylogenetical signal considering both extinct and extant families (Monson & Hlusko et al 2018;Gomes Rodrigues et al 2019). In this study, one character consists of the dental eruption pattern discussed in Gomes Rodrigues et al (2019;Figure 3A, Appendix 1), while the remaining 38 dental characters are new features (21 for the lower deciduous premolars, and 17 for the upper deciduous premolars, Figure 3B, C; Appendix 1).…”

“…The dental eruption pattern of cetartiodactyls has recently been studied and demonstrated as having a strong phylogenetical signal considering both extinct and extant families (Monson & Hlusko et al 2018;Gomes Rodrigues et al 2019). In this study, one character consists of the dental eruption pattern discussed in Gomes Rodrigues et al (2019;Figure 3A, Appendix 1), while the remaining 38 dental characters are new features (21 for the lower deciduous premolars, and 17 for the upper deciduous premolars, Figure 3B, C; Appendix 1). A new character related to p1 morphology was also added (character 17: p1 caniniform -17 0 No, 17 1 Yes), which brings to 221 the total number of characters in the new matrix (Appendix S1).…”

Paleoecological Inferences from Long Bone Microanatomical Specializations in Hippopotamoidea (Mammalia, Artiodactyla)

“…For this testing, we used two different consensus trees (Fig. 1) based on phylogenies from Lihoreau et al (2015Lihoreau et al ( , 2019, Boisserie et al ( , 2017, and Gomes Rodrigues (2019) for the relationships within Hippopotamoidea, the proposition of Thewissen et al (2007) and Vautrin et al (2020) for the position of Indohyus and Cetacea, and recent phylogenetic hypotheses based on molecular data for extant representatives of modern clades of laurasiatherian mammals (Gilbert et al 2006;Bibi 2013;Foley et al 2016;Springer et al 2019). These phylogenies differ by the relationships observed within Hippopotamoidea.…”

“…A from Boisserie et al (2011) for the hippopotamines, Lihoreau et al (2015; SI fig. 17) and Boisserie et al (2017) for the other hippopotamoids; B fromLihoreau et al (2015Lihoreau et al ( , 2019 and GomesRodrigues et al (2019) for the hippopotamoids, and A,B fromThewissen et al (2007)…”