New paroxyclaenid mammals from the early Eocene of the Paris Basin (France) shed light on the origin and evolution of these endemic European cimolestans

Abstract

We present new species of an enigmatic family of mammals, which is endemic to Europe, the Paroxyclaenidae: Merialus bruneti sp. nov., Fratrodon tresvauxi gen. et sp. nov., Paraspaniella gunnelli gen. et sp. nov., and Sororodon tresvauxae gen. et sp. nov. The fossils described come from six localities of the Ypresian of the Paris Basin (France): Pourcy (MP7), Mutigny, Avenay, Cond e-en-Brie (MP8 þ 9), Grauves and Pr emontr e (MP10). They allow the description of three new genera and four new species belonging to the subfamilies Merialinae and Paroxyclaeninae. Two of these new species represent the earliest occurrence of each subfamily. Fossils from Mutigny, Avenay and Cond e-en-Brie indicate that merialines were more abundant than paroxyclaenines during the Ypresian. Surprisingly, merialines disappeared from the fossil record at the end of the Ypresianthe youngest records are close to MP10while the paroxyclaenines were present in Europe until the end of the middle Eocene. Based on comparison with the data presently available for European mammals during the Ypresian, we suggest the existence of two periods of faunal turnover that must be more extensively studied in the future in order to be fully characterized: the 'Intra-Ypresian Mammal Turnover' and the 'Ypresian-Lutetian Mammal Turnover'. Finally, because the oldest paroxyclaenids appear morphologically closer to cimolestids such as Procerberus than to pantolestans, it is suggested that similarities between paroxyclaenids and pantolestans could be due to convergence. http://zoobank.org/urn:lsid:zoobank.org:pub:8A3B21A0-6945-4CE4-975C-402736E92C51

Evolution of European carnivorous mammal assemblages through the Palaeogene

“…Following BiochroM'97 (1997), MP17 is divided in MP17a and MP17b. For the absolute ages of the Paleogene stages and estimated ages of the MP levels, we used the Paleogene dates compiled by Speijer et al (2020) and plotted our data by using Time Scale Creator version 7.4 (TSCreator, 2020).…”

“…As indicated by both the FAD/LAD and the percentage of renewal (Supplementary Texts 1-2), the Ypresian as a whole was a period of instability for carnivorous mammal diversitynotably for hyaenodonts, which experienced higher turnover rates than carnivoramorphans. Other clades underwent profound changes as well, illustrated by the disappearances of viverravids and oxyaenids around 54-52 Ma (Intra-Ypresian Mammal Turnover; Solé et al, 2011Solé et al, , 2019b, and mesonychids at the end of the Ypresian (ca. 48 Ma; Ypresian-Lutetian Mammal Turnover; Solé et al, 2018Solé et al, , 2019b) (Fig.…”

“…Other clades underwent profound changes as well, illustrated by the disappearances of viverravids and oxyaenids around 54-52 Ma (Intra-Ypresian Mammal Turnover; Solé et al, 2011Solé et al, , 2019b, and mesonychids at the end of the Ypresian (ca. 48 Ma; Ypresian-Lutetian Mammal Turnover; Solé et al, 2018Solé et al, , 2019b) (Fig. 1B, Fig.…”

“…Other mammal groups radiated at the end of the Ypresian (MP10): perissodactyls, artiodactyls, rodents, and pantolestids (Savage et al, 1966;Sudre & Erfurt, 1996;Smith, 2001). However, these events are best seen as turnovers, being associated with a series of contemporaneous extinctions (Solé et al, 2019b). These extinctions and radiations might be related to the Early Eocene Climatic Optimum (EECO, ca.…”

“…They suggested that carnivoramorphans increase in size throughout the Eocene, and that the dietary diversity of carnivoramorphans increased throughout the Eocene, while that of the hyaenodonts decreased. In North America, carnivoramorphan genera clearly outnumbered other groups by the early Lutetian (= Uintan North American land mammal age; see Speijer et al, 2020). Friscia & Van Valkenburgh (2010) concluded that the replacement of 'creodonts' (i.e., Oxyaenidae and Hyaenodonta) by Carnivoraformes corresponds to a competitive replacement that might have been driven by the anterior position of the carnassial teeth in Carnivoraformes compared to the posterior position of carnassial teeth in oxyaenids and hyaenodontoids.…”