Praepusa boeska Koretsky, Peters et Rahmat, 2015

Koretsky, I. A., Peters, N. & Rahmat, S., 2015, New Species Of Praepusa (Carnivora, Phocidae, Phocinae) From The Netherlands Supports East To West Neogene Dispersal Of True Seals, Vestnik Zoologii 49 (1), pp. 57-66 : 60-63

Praepusa boeska Koretsky, Peters et Rahmat , sp.n. ( fig. 2–3 ; tables 1–2)

H o l o t y p e. Right humerus MAB 4686 (♀), collection of the Museum de Groene Poort , Boxtel (NL), found in Antwerp harbour ( Belgium), not in-situ. Miocene? The Antwerp Basin, Belgium .

P a r a t y p e. Sacrum RGM 629552, collection of the Naturalis Biodiversity Center in Leiden (NL). Miocene — Pliocene, The Antwerp Basin, Belgium.

E t y m o l o g y. boeska ,in reference to its finder Mr.K.A.Boes, The Netherlands (= Holland).

T y p e L o c a l i t y. The Antwerp Basin, Belgium.

R e f e r r e d m a t e r i a l. In addition to the type material, the following specimens were found in The Netherlands: Humeri MAB 4687, distal half of left humerus, Ơ; MAB 4688, distal half of left humerus, Ơ; MAB 4689, distal half of left humerus, cast, Ơ; MAB 4690, dis-

D E F

Рис. 2. Плечевые Praepusa boeska sp.n., голотип, MAB 4648, правая плечевая кость, самка, миоцен?, Антверпен бассейн, Бельгия: A — вид спереди; B — вид с латеральной стороны; C — вид с медиальной стороны; и MAB 4687, левая плечевая кость, самец, поздний миоцен — ранний плиоцен (тортонийпьяцензиан, 11,5–3,5 млн лет назад), песчаный подводный карьер «Де-Кёйлен» (муниципалитет Милл- Лангенбом), провинция Северный Брабант, юго-восточная Голландия; D — вид спереди; E — вид с латеральной стороны; F — вид сзади.

tal end of right humerus, ♀; MAB 4691, distal end of left humerus, cast, ♀. All referred material comes from the S. E. Netherlands, Noord-Brabant, Late Miocene — Late Pliocene (Tortonian–Piacenzian Stages, 11.5–3.5 Ma), sandpit de Kuilen, village of Mill-Langenboom .

D i a g n o s i s. Deltoid crest sharp-bladed and extends to 2/3 of humeral length, not reaching coronoid fossa; maximal width of deltoid crest located in its middle portion; lesser tubercle of humerus located slightly above proximal border of deltoid crest, round in shape and not deviated from humeral axis; head compressed medio-laterally; ratio of head width to its height 0.98; lateral epicondyle does not reach middle of diaphysis, but reaches distal part of deltoid crest.

Sacrum-based diagnosis is same as for the genus Praepusa described above.

Рис. 3. Крестец Praepusa boeska sp. n., RGM 629552, коллекция Национального центра биологического разнообразия в Лейдене (NL), занклиян–пьяцензиан (плиоцен), Антверпенский бассейн, Бельгия: A — вид снизу; B — вид сверху; C — вид спереди.

D e s c r i p t i o n. Small seal that has dimensions close to Recent Pusa .

Humerus ( fig. 2 ; table 1). The deltoid crest is long and slender, extending for about 2/3 of the length of the bone; the lesser tubercle is visible and is located distal to the head of the humerus, barely above the greater tubercle; it does not deviate from the humeral axis, is round in shape and well developed; the musculospiral groove is not expressed; the lesser tubercle is below the level of the head, but the intertubercular groove is very narrow and deep; the head is slightly compressed medio-laterally; the ratio of the head width to its height is 102 %; the deltoid crest has the form of a sharp blade and does not reach the condyles; the maximal width of the deltoid crest is in its middle part; the lateral epicondyle is well developed, reaches the distal part of the deltoid crest just below the middle of the diaphysis and extends twice as far proximally as the medial epicondyle; the medial epicondyle is flattened, spreading from the lower part of the entepicondylar foramen and ending at the middle of the coronoid fossa; the coronoid fossa is shallow and forms an oval in Ơ or triangular in ♀ depression extending proximally to the medial epicondyle, ending below the lateral epicondyle; the entepicondylar foramen is present, large and oval, open, but the narrow bridge over it is broken away; the olecranon fossa is very shallow in Ơ and deep in ♀. Detailed description of sexual dimorphism in the mandible and postcranial elements for the subfamily Phocinae ( Koretsky, 1987 a, 2001) and subfamily Monachinae (Koretsky, Ray, 2008) has previously been published.

Sacrum ( fig. 3 ; table 2). Consists of three fused vertebrae, with an absolute length of 63.0 mm and width of 57.6 mm. The maximum width of the wings is 86.2 % of the length of the sacrum, which according to Antoniuk (1979) is a diagnostic character of Phocidae . The sacral promontory is concave and not pronounced. The proximal surface of the first centrum is lower than the wings of the sacrum, a configuration that is similar to other Phocinae , including Leptophoca ( Antoniuk, 1979, table 2; Koretsky, 2001, table 13). The ala (= wing) is thin and higher than the proximal surface of the first centrum like in phocines, but in contrast to monachines where the ala is lower than the centrum ( Antoniuk, 1979). On S1–S3, a well-defined mammillo-articular process (= intermediate sacral crest) is present; S3 has a less developed mammillo-articular process. The median sacral crest, which is formed by several un-fused spinous processes, is very short and extends caudally. Dorsal and ventral sacral foraminae are equal in size.

According to sexual dimorphism in sacral bones described by Gadjiev (1982), RGM 629552 belongs to an adult male because its first ventral foramen is rounded and the lateral wall is very thick. The body of the sacrum is slender and narrow.

C o m p a r i s o n. The bones of the postcranial skeleton of Praepusa boeska are smaller than those of Pr. vindobonensis and Pr. magyaricus and are similar to those of Recent Pusa . In humeral morphology, the new species differs from Pr. vindobonensis and Pr. magyaricus in its lesser tubercle being positioned lower than the head, and slightly above the greater tubercle; deltoid crest being shorter, not reaching the condyles, and widest in its middle part; larger entepicondylar foramen; and coronoid fossa being shorter and terminating lower than the lateral epicondyle. In contrast to Pr. magyaricus , the humerus of Pr. boeska has a head that is medio-laterally compressed.

D i s c u s s i o n. Antoniuk and Koretsky (1984) previously assigned the seal from Tarchankut Peninsula ( Ukraine) to the genus Praepusa , species tarchankutica . They described an almost complete skeleton, mandible, and skull belonging to a subadult individual in comparison with another skull belonging to an adult individual. The mandible is very similar to Praepusa vindobonensis Toula 1897 , and for this reason the name tarchankutica , as a junior synonym, is no longer valid ( Koretsky, 2001).

Only few fossil sacral bones of the subfamily Phocinae have been described or illustrated previously. These include: Pusa caspica ( Gadjiev, 1982) , Phocanella , “ Phoca ” and Prophoca (Van-Beneden, 1877; Atlas pl.14; 15; 18), and Leptophoca ( Koretsky, 2001; 2006). Several sacral bones have been described from the subfamily Monachinae : Callophoca (Koretsky, Ray, 2008) , Monaterium (Van-Beneden, 1877; Atlas pl.16), Acrophoca (de Muizon, 1981) and several sacral bones are known from the Subfamily cystophorinae (Koretsky, Rahmat, 2013). However, the rather well-preserved condition of the found Praepusa sacrum from the Western Paratethys, and its morphologically distinguishing characteristics make it possible to separate this bone from other phocine species from the other areas of the Paratethys.

G e o l o g i c a l a g e a n d d i s t r i b u t i o n. Eastern shore of the Atlantic Ocean (Western Europe); Late Miocene (early-middle Tortonian Stage) — Pliocene (Zanclian– Piacenzian Stages) sandpit “de Kuilen”, Mill-Langenboom, 11.5–3.5 Ma, Noord-Brabant, S. E. Netherlands. Late Pliocene (Scaldisian), Anvers 3rd Section, Antwerp Basin, Belgium.

Figures

Fig. 2. Humeri of Praepusa boeska sp. n., MAB 4686 holotype, right humerus, female, Miocene? the Antwerp Basin, Belgium: A —cranial view; B — lateral view; C — medial view; and MAB 4687, left humerus, male, Late Miocene — Early Pliocene (Tortonian–Piacenzian Stages, 11.5–3.5 Ma), sandpit de Kuilen (municipality of Mill-Langenboom), Noord-Brabant, S. E. Netherlands; D — cranial view; E — lateral view; F — caudal view.

Fig. 3. Sacrum of Praepusa boeska sp. n., RGM 629552, collection of the Naturalis Biodiversity Center in Leiden (NL). Zanclian–Piacenzian (Pliocene), Antwerp Basin, Belgium: A — ventral view; B — dorsal view; C — cranial view.