Hallensia parisiensis Franzen, 1990

Bronnert, Constance & Métais, Grégoire, 2023, Early Eocene hippomorph perissodactyls (Mammalia) from the Paris Basin, Geodiversitas 45 (9), pp. 277-326 : 303-304

Hallensia parisiensis Franzen, 1990

( Fig. 14 )

Hallensia parisiensis Franzen, 1990: 193-195 .

Propachynolophus gaudryi – Savage et al. 1965: 16, 19, 21 (partim), fig. 7.

Propachynolophus sp. – Louis et al. 1983: 12.

HOLOTYPE. — NMB.TS-631 , fragmentary maxillary with P4-M1 .

PARATYPE. — NMB.TS-367 , fragmentary maxillary with DP2-DP3 .

MATERIAL. — Condé-en-Brie: maxillary P3-M1 (R: MNHN-CB1529); DP3 (R: MNHN-CB1557; L: IRSNB M 2304 [Lepage collection in Hooker 1994]); P2 (R: MNHN-CB1562) .

Saint-Agnan: P2 (L: MNHN-STA636); m1/2 (R: MNHN-STA625- L; L: MNHN-STA623-L) .

Fossoy (MP 10): mandible p4-m3 (L: coll. Lhomme) .

TYPE LOCALITY. — Monthelon (Marne, France), MP10.

DISTRIBUTION. — Condé-en-Brie (Marne, France), MP8-9; St Agnan, Monthelon (Marne, France), MP10.

EMENDED DIAGNOSIS. — Well-developed paraconule and metaconule of upper premolars and molars; reduced parastyles; large lower molars; cingulums large and continuous.

DIFFERENTIAL DIAGNOSIS. — Smaller species than H. matthesi . Conules more developed than in Cymbalophus , Pliolophus , Hyracotherium and Orolophus . Teeth more rounded in occlusal view.

DESCRIPTION

Teeth

The P2 is almost sub-circular in occlusal view ( Fig. 14B ). The parastyle is very small. The paracone and the metacone are close. The protocone is large and linked to the preparacrista by a well-developed protoloph. The cingulum forms a crest starting from the protocone and joining the metastyle. A small postprotocrista is present. The P3 is triangular in occlusal outine, and the cusps are rounded ( Fig. 14A ). The paracone and metacone are close. The protocone is large and the paraconule is a little smaller. The protoloph is interrupted before joining the preparacrista. The parastyle is very poorly developed. The P4 is triangular in occlusal view and is not molarized ( Fig.14A, F ). The parastyle is absent (NMB.TS-631, Fig. 14F ) or poorly developed (MNHN-CB1529, Fig. 14A ). The paracone and the metacone are close and of the same size. The centrocrista is straight ( Fig. 14A ) or flexed labially with a faint rib mesostyle ( Fig. 14F ). The paraconule is almost as developed as the main cusps. The protoloph joins the preparacrista. A small metaconule can be present, connected to the protocone by the postprotocrista, as well as to the anterior part of the metacone ( Fig. 14F ), or very reduced ( Fig. 14A ). An endoprotocrista is present posterior to the protocone. The cingulum is continuous all around the tooth. The parastyle of M1 is absent ( Fig. 14F ) or poorly developed ( Fig. 14A ). The paraconule and the metaconule are present but much worn on the upper teeth. The centrocrista is labially flexed. A crest is present at the position of the mesostyle, it forms an extension of the premetacrista. The cingulum is interrupted lingual to the hypocone and labial to the paracone.

The lower molars are wide, the lophs are well developed. The hypoconulid is linked to the hypoconid (MNHN-STA623, Fig. 14C ) or hypolophid (MNHN-STA625; Fig. 14E ). The metaconid is twinned. The cristid obliqua is oriented toward the center of the protolophid. The m3 has the same morphology as other molars, only the hypoconulid lobe is more developed ( Fig. 14H ). The hypoconulid is linked to the hypoconid by a postcristid.

Deciduous teeth

DP1/P1: The first premolar is not known but the alveoli indicate a biradiculate tooth and a post-canine diastema of unknown length ( Fig. 14G ). The metacone of DP2 is much more worn than the paracone ( Fig. 14G ). The parastyle is developed and projected anteriorly. A protoloph runs from the preparacrista but is interrupted before joining the protocone. The protocone is shifted posteriorly and it is connected to the paracone by a crest.A small metaconule is present.The DP3 is sub-molariform ( Fig. 14G ). The parastyle is present.The centrocrista is straight ( Fig. 14D ) or labially flexed ( Fig. 14G ). The paraconule and the metaconule are very small. The protoloph is developed and joins the preparacrista. The metaloph is developed and joins the anterior side of the metacone without interruption. The hypocone is slightly larger than the protocone.The cingulum s is well marked, but it tends to become thinner or absent below the hypocone and paracone in some specimens ( Fig. 14G ).

COMPARISONS

Hallensia parisiensis is larger than Cymbalophus , Pliolophus , Hyracotherium , O. maldani and Hallensia louisi , but smaller than Hallensia matthesi . The teeth have a typical inflated appearance, absent in other genera. The centrocrista of molars is slightly straighter than in Orolophus and Hyracotherium . A small-ridged mesostyle can be present, as in Hyracotherium , Orolophus and P.gaudryi . The postcristid of the lower molars presents the same morphology as in Pliolophus and Cymbalophus . The labial cingulids are more developed in Hallensia . The third lobe of m3 is longer in Hallensia than in Cymbalophus . The cristid obliqua of m3 is more labial in C. cuniculus and Pliolophus than in H. parisiensis .

COMMENT

The fossils of Condé-en-Brie, St Agnan and Sézanne are slightly smaller than the holotype from Monthelon. The centrocrista is straight and the lophs are less developed than in the holotype. These features are more primitive than those of the type specimen. As this species is poorly known, the creation of a new species solely on the basis of the incomplete material is not sufficient at this point. In addition, these differences could be due to intraspecific variation. This latter hypothesis is favoured and the fossils are therefore attributed to H. parisiensis .

Figures

FIG. 14. — Teeth of Hallensia parisiensis Franzen, 1990 from the Paris Basin in occlusal view: A, right maxillary with P3-M1 (MNHN-CB1529); B, right P2 (MNHN- CB1562); C, left m1/2 (MNHN-STA623 [reversed]); D, right DP3 (MNHN-CB1557); E, right m1/2 (MNHN-STA625); F, right maxillary P4-M1 (cast of holotype, NMB-TS-631); G, right maxillary with DP2-DP3 (cast of paratype, NMB-TS-367); H, right mandible with p4-m3 (coll. Lhomme). Scale bar: 5 mm.