Cartierodon egerkingensis, Solé & Mennecart, 2019

Solé, Floréal & Mennecart, Bastien, 2019, A large hyaenodont from the Lutetian of Switzerland expands the body mass range of the European mammalian predators during the Eocene, Acta Palaeontologica Polonica 64 (2), pp. 275-290 : 277-280

Cartierodon egerkingensis sp. nov.

Fig. 2.

ZooBank LSID: urn:lsid:zoobank.org:act:9D682E10-CF2A-4C0F-B9C5-1A00626FB753

Etymology: Refers to the type locality, the filling of Egerkingen γ.

Holotype: NMB.Em.11, right mandible bearing p2, p3, p4, the trigonid of m1, and the alveoli of p1.

Type locality: Egerkingen γ, Gaü, Solothurn, Switzerland.

Type horizon: Unnamed unit of karst fillings in an aberrant siderolitic facies; MP13?, Lutetian, Eocene.

Material.— NMB.Ee.126a, Lp 1; NMB.Eh.550, left maxillary bearing P2 and distal root of P1; NMB.Ek.42, RDP4; NMB. En.78, RP2; NMB.En.80, LP3; NMB.En.85, RP4; NMB. En.86, RM 2; NMB.En.87, RM 2; NMB.En.88, LM; NMB. En.90, RM 2; NMB.En.91, Rp 2; NMB.En.92, Rp 2; NMB. En.93, Rp 3; NMB.En.94, Lp 3; NMB.En.95, Lp 3; NMB. En.96, Lp 4; NMB.En.97, Rp 4; NMB.En.98, Rm 3; NMB. En.99, left mandible bearing m2 and the trigonid of the m3; NMB.En.100, Lm 3; NMB.En.134, Rp 4; NMB.En.152, Lm 3; NMB.En.153, LP3; NMB.En.154, LM1; NMB.En.155, Rdp 4; NMB.En.156, Rm 2; NMB.En.213, Rdp 3; NMB. En.215, Rm 1; NMB.En.216, Rm 2; NMB.En.217a, Lm 2. From the type locality .

Diagnosis.—DiffersfromallcontemporaneousEuropeanhyaenodontgenera( Oxyaenoides , Proviverra , Cynohyaenodon , Eurotherium , Prodissopsalis , Leonhardtina , Allopterodon , Alienetherium , and Praecodens ) by its larger size. It differs from Oxyaenoides by the presence of a metaconid on molars and transversally enlarged premolars. It also differs from Proviverra , Cynohyaenodon , Eurotherium , Leonhardtina , Allopterodon , Alienetherium , and Praecodens by a poorly developed metaconid on molars. It differs from Quercytherium , with which it shares transversally enlarged premolars, by its larger size, poorly developed metaconid on molars, and less squared p2 and p3. It differs from Prodissopsalis eocaenicus , its closest hyaenodont relative, by a second foramen located below the anterior root of the p4, wider lower premolars, mesiodistally shorter talonid on m3, and a protocone area more developed on P3.

Description.—The mandible is deep (≈ 36 mm; Table 1). The symphysis extends below the mesial root of the p3. The first foramen opens below the anterior root of the p2, while the second foramen is located below the anterior root of the p4.

We identified two lower deciduous premolars: one dp3 (NMB.En.213) and one dp4 (NMB.En.155). The two teeth are mesiodistally elongate. The dp3 is characterized by a large but low paraconid, and by individualized hypoconid, hypoconulid, and entoconid. The dp4 is characterized by the absence of contact between the paraconid and metaconid, the two cusps being separated by the protoconid. The metaconid was probably smaller than the paraconid; it is distally located compared to the protoconid. The talonid is mesiodistally short and wide. It bears the three usual talonid cusps. The hypoconulid bears two distinct apexes (i.e., cuspulation).

All the permanent teeth have crenulated enamel. The premolars are characterized by a transversally enlarged but mesiodistally short talonid. The p1 has two roots. The anterior root is curved in lateral view (Fig. 2M 2, M 3): this may indicate that the p1 was very close to the canine. The paraconid is characterized by a very thin fold in the mesial part of the tooth. A thin transversally aligned crest is visible at the posterior part of the talonid, marking the talonid region. The very small crest bears a cusp (hypoconid?). The p2 is longer and wider than the p1, but it is morphologically similar to the p1. The p3 is obliquely implanted on the holotype ( NMB.Em.11; Fig. 2L 1). The p3 differs from the p1 and p 2 in having an individualized paraconid. The talonid is transversally extended and bears a large hypoconid. The presence of the entoconid is variable: the entoconid is absent on NMB.En.95, while it is present on NMB.En.94; and two cusps are present on the lingual part of the talonid on NMB. En.93. The p4 is very similar to the p3, but differs in having larger paraconid, hypoconid, and entoconid. However, the p4 is slightly mesiodistally shorter than the p3, a feature visible on the holotype NMB.Em.11 (15.63 mm vs. 15.19 mm) .

The m1 displays a very small metaconid; the cusp is lower than the paraconid. The paraconid is well mesially located. The paraconid has a sharp mesial crest and possesses a small anterior keel visible on its buccal aspect. The metaconid is distally located compared to the protoconid, but is not as distally located as on the dp4. Moreover, the metaconid and paraconid are not separated by the protoconid. The talonid is mesiodistally short; the postfossid is shallow and narrow. One can observe the entoconid, hypoconid, and hypoconulid on the talonid; the hypoconid is slightly higher than the two other talonid cusps. The precingulid is short but wide. The m2 is similar in morphology to the m1. It differs in being taller and in being longer and wider. Like m1 and m2, the m3 displays a secant trigonid characterized by a mesially located paraconid and small metaconid; the latter is transversally aligned with the protoconid on m3. The protoconid of the m3 is more retroflexed than on m1 and m2. The talonid is mesiodistally shorter and narrower than on the m1 and m2. The specimen NMB.En.100 (isolated m3) is interesting in having only one large root: the anterior and posterior roots are not entirely separated (Fig. 2I 2). Moreover, one can note the presence of a single cusp on the talonid.

A DP4 has been identified (Fig. 2A). The tooth is mesiodistally elongated. The paracone and metacone are well separated. The metacone is larger than the paracone. A weak parastyle is present. The metastyle is long and mesiodistally aligned. The protocone is mesiodistally short and narrow. The paraconule and metaconule are present. There is no internal crest in the trigon basin. The metaconule and metastyle are not linked by the metacingulum.

The upper premolars are wide. The P1 is unknown but has two roots based on the alveoli present on NMB.Eh.550 (Fig. 2H). There is a short separation between the P1 and P2. The P2 does not display a parastyle. The metastyle is very small. On NMB.Eh.550, one can notice that the P2 has three roots. The P3 (Fig. 2G), which also has three roots, notably differs from the P 2 in having a larger lingual fold. There is no parastyle; the metastyle is larger than on P2. The P4 has an individualized protocone and a strong parastyle. The metastyle is mesiodistally short, high, and secant. It displays two cusps on NMB.En.81 and NMB.En.85. A cingulum links the metastyle and the protocone. The protocone is long but narrow; it does not show any accessory cusp.

The M1 and M2 are incompletely known. They are morphologically very similar; the M2 is longer than the M1 ( Table 1). The paracone and metacone are less separated than on the DP4; only the apices of the cusps are separated. The paracone is clearly smaller and mesiodistally shorter than the metacone. The metastyle is as long as the metacone–paracone base. It is distally shifted. The parastyle is more developed on the M2 than on the M1. The protocone is unknown for the molars; because the postfossid on the molars are shallow and narrow, the protocone of the molars could have been narrow and low.

Discussion.—The new taxon is represented mostly by isolated teeth. We consider that they represent the same taxon because they are from the same locality (i.e., Egerkingen), because of their similar morphology (e.g., secant morphology of the molars, transversal enlargement of the premolars), and because of their large size compared to the other hyaenodonts found at Egerkingen.

The new taxon resembles the hyaenodonts recording in the Ypresian and Lutetian of Europe ( Proviverra , Cynohyaenodon , Eurotherium , Prodissopsalis , Leonhardtina , Allopterodon , Alienetherium , Quercytherium , and Paracynohyaenodon ) because of the presence of a two-rooted p1, of a paraconid and an entoconid on p3 and p4, of a large protocone

Fig. 2. Hyaenodontid mammal Cartierodon egerkingensis gen. and sp. nov. from Switzerland, Egerkingen γ (MP13?, Lutetian, Eocene). A. NMB.Ek.42, → DP 4 in occlusal (A 1) and labial (A 2) views. B. NMB.En.213, dp 3 in occlusal (B 1), labial (B 2), and lingual (B 3) views. C. NMB.En.155, dp 4 in occlusal C 1), labial (C 2), and lingual (C 3) views. D. NMB.En.87, M 2 in occlusal (D 1), lingual (reversed, D 2), and labial (D 3) views. E. NMB.En. 154 in occlusal reversed, E 1), lingual (E 2), and labial (reversed, E 3) views. F. NMB.En.85, P4; in occlusal (F 1), lingual (reversed, F 2), and labial (F 3) views. G. NMB. En.80, P 3 in occlusal (reversed, G 1), lingual (G 2), and labial (reversed, G 3) views. H. NMB.Eh.550, maxillary bearing P2 and distal root of P 1 in occlusal reversed, H 1), lingual (H 2), and labial (reversed, H 3) views. I. NMB.En.100, m 3 in occlusal (reversed, I 1), labial (reversed, I 2), and lingual (I 3) views.. NMB.En.216, m 2 in occlusal (J 1), labial (J 2), and lingual (reversed, J 3) views. K. NMB.En.215, m 1 in occlusal (K 1), labial (K 2), and lingual (reversed, K 3) views. L. NMB.Em.11, mandible bearing p2, p3, p4 and the trigonid of m1, and the alveoli of p1, in occlusal (L 1), labial (L 2), and lingual (reversed, L 3) views. M. NMB.Ee.126a, p 1 in occlusal (reversed, M 1), labial (reversed, M 2), and lingual (M 3) views.

area on the upper premolars, and of an individualized entoconid on molars.

The transversal enlargement of the premolars and the position of the mental foramina recall the European hyaenodont genus Matthodon . This genus is represented by two species: Matthodon menui from Cuis, Chavot, Monthelon, Mancy, and Grauves (Ypresian, MP10; France) and Matthodon tritens from Geiseltal-Untere Unterkohle (Lutetian, MP11; Germany) ( Lange-Badré and Haubold 1990; Solé et al. 2014). The specimens from Egerkingen γ, however, differ in having less bulbous premolars, a larger metaconid, and a two-rooted p1. The presence of the metaconid on molars also distinguishes the Swiss fossils from those of Oxyaenoides Crochet et al. 1988 ; Lange-Badré and Haubold 1990; Solé et al. 2014, 2015).

The general morphology of the new fossils is most similar to Prodissopsalis eocaenicus . This species is known from Geiseltal-Untere Mittelkohle (MP12), Geiseltal-Obere Mittelkohle (MP13), Issel (MP14), and Lissieu (MP14) ( Matthes 1952; Calas 1969, 1970; Lange-Badré 1972; Lange-Badré and Haubold 1990), see below for a discussion concerning the fossils from Lissieu. The new species and Prodissopsalis eocaenicus actually share the transversally enlarged upper and lower premolars, the p3 as long as the p4, the presence of a poorly developed metaconid on molars, the presence of mesiodistally short but wide talonid on molars, the reduction of the talonid of the m3, and the small size of the paracone.

The taxon described herein differs from Prodissopsalis eocaenicus by a second foramen located below the anterior root of the p4, wider lower premolars (Fig. 2), mesiodistally shorter talonid on m3, and a protocone area more developed on P3.

Surprisingly, the obliquely implanted p3, visible on the holotype (NMB.Em.11), recalls the fossils of Prodissopsalis eocaenicus from Geiseltal-Untere Mittelkohle (MP12) rather than those from Geiseltal-Obere Mittelkohle (MP13) (see Lange-Badré and Haubold 1990 for a discussion concerning this feature). This feature (i.e., obliquely implanted p3) is also visible in the late Eocene Paenoxyaenoides liguritor ( Lange-Badré 1979) . It possibly traduces a common feature; however, it is possibly related to an anteroposterior shortening of the mandible and thus could represent a convergent feature.

The new taxon shares with Paenoxyaenoides liguritor the transverse enlargement of the lower premolars. However, Paenoxyaenoides differs from the Egerkingen species by the absence of the metaconid on the molars (derived feature), the position of the mental foramina, below p1 and p3, and the P3/p3 distinctly mesiodistally shorter than the P4/p4 ( Fig. 3 ).

The fossils here described are also characterized by sizes that are larger than those of the hyaenodonts previously known in the Lutetian of Europe. Until the discovery of this new hyaenodont, the largest European hyaenodonts recorded for this period were Matthodon tritens , Prodissopsalis eocaenicus , and Oxyaenoides schlosseri : the length of the molar row (m1 to m3) for each of these taxa equals 39.5 mm ( Lange-Badré and Haubold 1990), 38.8 mm ( Van Valen 1965), and 38.12 mm ( Solé et al. 2015). Because the molar row of Cartierodon egerkingensis equals roughly 43.5 mm, the new fossils represent the largest hyaenodont ever discovered in the Lutetian of Europe.

As a result, the fossils housed at the NMB correspond to a new hyaenodont taxon. We thus propose to refer all these dental elements to a new genus and new species: Cartierodon egerkingensis .

Stratigraphic and geographic range.—Egerkingen γ ( Switzerland; MP13?, Lutetian, Eocene).

Figures

Fig. 3. Comparison of the length of the lower premolars and molars of Cartierodon egerkingensis gen. et sp. nov. from the Eocene of Switzerland, Egerkingen γ (MP13?); Prodissopsalis eocaenicus from the Eocene of Switzerland, Geiseltal-Obere Mittelkohle (MP12) and Geiseltal-Untere Mittelkohle (MP13) (based on Lange-Badré and Haubold 1990: table 3); and Paenoxyaenoides liguritor from the late Eocene of France, Quercy Phosphorites (based on Lange-Badré 1979: table 10).