Amphiperatherium frequens ( VON MEYER, 1846 )

Bonilla-Salomón, Isaac, Cailleux, Florentin, Joniak, Peter, Ivanov, Martin & Sabol, Martin, 2024, Herpetotheriidae, Talpidae, And Erinaceidae From The Early Miocene Fissures Of Mokrá-Quarry (South Moravia, The Czech Republic), Fossil Imprint 80 (2), pp. 269-284 : 272-273

Amphiperatherium frequens ( VON MEYER, 1846)

Text-fig. 3

S t u d i e d m a t e r i a l a n d m e a s u r e m e n t s. MWQ2/2003: one P3 (Pal. 3538: 1.76×0.68); one fragment of upper premolar (Pal 3542); one left M2 (Pal. 3546: 2.05×2.15); one right M4 (Pal. 3547: 1.95×2.45); one left p1 (Pal. 3511: 1.47×0.67); one left p2 (Pal. 3515: 1.83×0,85); one left p3 (Pal. 3513: 1.9×0.89); one fragment of right m4 (3512).

MWQ4/2018: one fragment of left mandible with fragment of m3 and m4 (Pal. 4204: m4: 2×0.93).

D e s c r i p t i o n. P3. The tooth is labiolingually compressed. The main cusp is in a central position. The anterior cuspule is small. There is a well-developed crest that connects the main cusp to the posterior margin of the tooth. A posterior cingulum is present.

M2. The tooth has a subtriangular outline in occlusal view. The ectoflexus is concave between the antiparacone and antimetacone; there is no anticone between both cusps ( Text-fig. 3a). The parastyle is distinct and isolated from the antiparacone. The metacone is higher than the paracone, and both cusps are connected by the premetacrista and the slightly shorter postparacrista. The postmetacrista is elongated and curved. The metastyle is indicated. The paracingulum is straight. The trigon basin is wide. The protocone is connected to the base of the paracone and metacone by two almost symmetrical crests. Three roots are preserved; the lingualmost is the thickest.

M4. The two-rooted tooth has a triangular outline in occlusal view and is strongly reduced in length. The paracone is conical and elongated. From it, the preparacrista runs labially to the parastyle. The parastyle is elongated lingually. The postparacrista and the premetacrista are connected. The metacone is small, protruding posteriorly. The protocone is the largest cusp ( Text-fig. 3b). The preprotocrista runs labially, ending at the base of the paracone. There is a postprotocrista running towards the metacone, without reaching it. The paracingulum begins near the very base of the paracone and joins the parastyle.

p1. The tooth has two roots. The main cuspid is in anterior position. The posterior cristid starting from this cuspid is labially oriented and turns posterolingually to reach the posterior talon, where a small cuspid is visible ( Text-fig. 3c).

p2. The posterior cingulid is large. Its lingual side is wider and concave. There is a small but distinct posterior cuspid.

p3. The two-rooted tooth has a thick main cuspid and a short postcingulid. There is no anterior bulge.

m3. The protoconid is the only preserved cuspid of the trigonid. The protolophid appears to be complete. The hypoconid is anterior to the entoconid. The postcristid runs slightly posteriorly.

m4. In Pal. 3512, only the elongated talonid is preserved. The entconid is well-preserved, as an enlargement of the entocristid. The postentocristid is low and connects to a strong hypoconulid ( Text-fig. 3d). The hypoconid is worn. The postcristid is oblique, connecting the two posterior cuspids. Pal 4204 m 4 shows a well-developed anterior cingulid. The paraconid is well-developed. The paralophid shows a moderate central notch. The talonid is much narrower than the trigonid ( Text-fig. 3e). The hypoconid is in a slightly more anterior position than the entoconid. The entocristid and the oblique crista run anteriorly, the first one ending at the base of the metaconid and the second one at the meeting point of protoconid and metaconid.

Fragment of mandible. Pal. 4204 preserves part of the mandible carrying m3 and m4. The ramus horizontalis is high, with flat sides. It shows a wide lingual foramen below the posterior root of the m3.

R e m a r k s. The Herpetotheriidae TROUESSART, 1879 is a fossil family of the infraclass Metatheria, with no extant relatives. This family ranges from the Late Cretaceous to the Middle Miocene (for a complete literature review of the Herpetotheriidae , see Klietmann 2013). Herpetotheriids were classically placed within the Didelphidae GRAY, 1821 until Kirsch et al. (1997) gave them a family rank within Marsupialia . Ladevèze et al. (2012) considered that the morphological characters that differentiate Amphiperatherium from Peratherium AYMARD, 1850 are very variable, and consequently not diagnostic enough, as already noted by von Koenigswald (1970). Later, Lavedèze et al. (2020) reviewed the relationship between both genera, and its phylogenetic analysis suggests a close relationship between Amphiperatherium and Peratherium , establishing the subfamily Peratheriinae to include both genera.

Of all the Herpetotheriidae , Amphiperatherium is the only genus that occurs in Early Miocene European localities. Amphiperatherium was first recorded in Europe during the Eocene, a period when the genus reached its highest specific diversity ( Crochet 1980). After that, the genus gradually lost diversity, finally becoming extinct during the Middle Miocene ( Furió et al. 2012). The presumed last occurrence of this genus was reported from Ergeten (MN 7+8, Switzerland; Kälin and Kempf 2009). However, as discussed by Prieto and Rummel (2015), the faunal lists provided by Kälin and Kempf (2009: 124) “do not reflect reality”. Therefore, Prieto and Rummel (2015) consider that the last occurrence of Amphiperaterium in Swiss territory belongs to the Megacricetodon gersii - M. similis interval zone, between 14 and 14.2 Ma ago, which is in agreement with the German findings.

Amphiperatherium frequens has been recorded in many Central European localities from the Miocene, when environmental conditions were rather humid, although remains of the species have also been found in humid Spanish localities ( Furió et al. 2012). However, based on Crespo et al. (2020), Amphiperatherium might also have survived in rather dry environments.

Regarding MN 4 sites in Central Europe, remains of Amphiperatherium frequens have been found in several localities ( Ziegler and Fahlbusch 1986, Ziegler 1998a). In Czech sites, A. frequens has been found in Tuchořice and Ahníkov I, both MN 3 sites ( Fejfar et al. 2003) and Dolnice 1–3 (MN 4; Fejfar and Roček 1988). However, no detailed descriptions of the species in these assemblages have been ever published. Therefore, the Amphiperatherium remains from Mokrá-Quarry constitutes the first detailed description of the genus in the Czech Republic.

ThemarsupialspeciesfromMWQ2/2003andMWQ4/2018 clearly belong to Amphiperatherium frequens , which can be distinguished by the presence of a slender cristid in the talonid basin only interrupted by a small notch between entoconid and hypoconulid ( Text-fig. 3d, e), among other traits. The measurements fit well within the material from other Central European localities, such as Erkersthofen, Wintershof-West and Petersbuch 2 (all Germany; see Klietmann 2013: fig 5). Based on the size differences and morphological variability of A. frequens during the Early Miocene, von Koenigswald (1970) erected three subspecies, which were not followed by Crochet (1980). Furthermore, Ziegler and Falhbusch (1986) pointed out several dental characters, which together with size reduction indicate evolutionary degrees in A. frequens . Later, Ziegler (1990) used these subspecies as chronosubspecies. The omnipresence of a conical antimetacone on the M2, as observed in Pal. 3546 ( Text-fig. 3a) in the entire population instead of only a bicuspid one, is a tendency observed in the population sequence of Wintershof-West – Petersbuch 2 – Erkersthofen 1. Moreover, the M2 from MWQ2/2003 resembles morphologically, as in size, the single M2 recovered from Oberdorf 4 ( Ziegler 1998a: pl. 3, fig. 6). However, the scarcity of the remains found in the assemblage MWQ2/2003 hampers any inference of its evolutionary stage.