Plesiodimylus sp.

Van Den Hoek Ostende, Lars W., Casanovas-Vilar, Isaac & Furió, Marc, 2020, Stuck in the middle. A geographical appraisal of the oldest insectivores - and a marsupial - from the Vallès-Penedès Basin (early Miocene, Catalonia, Spain), Comptes Rendus Palevol 19 (1), pp. 1-25 : 12-13

Plesiodimylus sp.

( Fig. 4 H-K)

MATERIAL AND MEASUREMENTS (in cm). — Spain. Can Julià , 1 m 2 sin., IPS86237 , 2.53 × 1.36 ; Sant Andreu de la Barca 1, 1 mandible with c-m2 sin., IPS86185 , c – × –; p1 1.29 × 0.81; p2 0.66 × 0.66; p3 0.67 × 0.71; p4 1.33 × 0.92; m1 2.12 × 1.32; m2 2.24 × 1.27 ; Turó de les Forques , 1 M2 dext., IPS85481 , 1.80 × 2.35 ; Costablanca 2, 1 m 2 sin., IPS85668 , 2.51 × 1.34 ; Can Martí Vell II, 1 M2 dext., IPS86256 , 2.05 × 2.49; 1 m 1 sin., IPS86258 , 2.31 × 1.45 .

DESCRIPTION

M2

The second upper molar from Turó de les Forques is hardly worn and slightly damaged in the parastylar region. The specimen from Can Martí Vell II is rather complete. The outline of the occlusal surface is triangular. The massive protocone has a faint crest between its tip and the base of the paracone. The two arms of the paracone stand at nearly a right angle; the anterior arm is not strongly elongated. The separate cusps of the mesostyle are still discernible in the specimen from Turó de les Forques, but would merge already at an early wear stage as they are in the element from Can Martí Vell II. The metacone is large and shaped as a curved ridge. Its arm is thickened just in front of the tip. The anterior face of the metacone slopes gently towards the protocone, the posterior side is much steeper.

Mandible

Only the horizontal ramus is preserved. The ventral margin is rather straight but there is a slight constraint under the p4 and m1. The mental foramen is covered by sediment, but it makes a shallow concavity under the trigonid of the m1. The symphyseal area covers the lingual side from the c to the anterior tip.

c

The only specimen is damaged, missing part of the anterolingual region. The preserved part shows a relatively narrow cingulum, which slopes up at the back of the tooth.

p1

The outline is subtriangular,with convex lingual and labial sides. The main cusp is massive and has its tip in the front part of the premolar. The cingulid is thickest along the posterior side and tapers out along the lingual and labial sides. It is missing at the very front of the premolars.

p2 + p3

The second and third lower premolar are similar in morphology, the p2 being slightly larger.The premolars are much wider than long, with a subelliptical outline. The central cusp is low. The cingulid appears widest at the posterior sides. In the p3, it surrounds the tooth; in the p2, it appears to be missing on the anterior side.

p4

The last premolar is set obliquely in the mandible. Its occlusal outline is elliptical. The tip lies far to the front of the premolars; the centrocristid is blunt. The p4 is surrounded by a cingulid that is of the same thickness throughout, but appears to be missing at the very front of the tooth.

m1

The only available specimen is heavily worn, obliterating all the details of the cusps. The trigonid is clearly longer than the talonid, but of the same width. The anterior side of the molar is rounded. The cingulid is well developed on the labial side. It tapers out halfway the posterior side and is missing along the anterior side of the molar.

m2

The second lower molar shows a slight degree of amblyodonty, but the ridges are relatively sharp. The talonid is somewhat shorter and narrower than the trigonid. The trigonid valley has its deepest point just behind the paraconid. The paralophid is curved and incorporates the paraconid completely. It reaches its farthest point about halfway the width of the molar, after which it curves back and becomes quickly lower. The posterior arm of the protoconid curves slightly backward before reaching the metaconid. The latter bears a very short metacristid. The talonid basin is very shallow, and is surrounded by a ridge, in which only the entoconid stands out a bit. The molar has a very strong anterior cingulid, which rapidly grows thinner near the base of the protoconid, but it still is well developed on the labial side, and ends halfway the posterior face of the talonid.

REMARKS

In contrast to Chainodus , Plesiodimylus is a relatively unspecialised dimylid. Its ability to deal with a wider range of environments may explain why this genus had the largest stratigraphic and geographic distribution in its family ( Furió et al. 2011a; Crespo-Roures et al. 2018). Plesiodimylus is known from Germany ( Müller 1967; Stephan-Hartl 1972; Schötz 1985; Ziegler & Fahlbusch 1986; Ziegler & Mörs 2000; Ziegler 1990a, 2005; Klietmann et al. 2014b), Austria ( Ziegler 2006a, b), Slowakia ( Fejfar & Sabol 2009), Czech Republic ( Van den Hoek Ostende & Fejfar 2015), Switzerland ( Bolliger 1992; Kälin & Engesser 2001), Poland ( Rzebik-Kowalska 1996), Greece ( Doukas 1986) and Turkey ( Engesser 1980). In Spain, Plesiodimylus is a quite common element in the late middle Miocene and early late Miocene faunas of the Vallès-Penedès ( Furió et al. 2011a, b; Van den Hoek Ostende et al. 2016), but had not been recognized from the early Miocene until recently, when Crespo-Roures et al. (2018) described a new species, P. ilercavonicus . Hitherto, the occurrences of this species are restricted to the type locality of Mas d’Antolino B-5 (early Aragonian) and the nearby sites of Barranc de Campisano 1 and Mas d’Antolino B 11 ( Crespo-Roures et al. 2019). Metrically, the Vallès-Penedès material is smaller than this species and comparable in size to P. aff. chantrei from Petersbuch 28 ( Klietmann et al. 2014b). Notably, there appear some differences particularly in the anterior dentition, such as the relatively shorter p1, the p2> p3 and the obliquely set p4. Given the limited material, these elements are for the moment best classified as Plesiodimylus sp.