Gryphoca nordica Koretsky, Rahmat et Peters, 2014

Koretsky, I., Rahmat, S. & Peters, N., 2014, Rare Late Miocene Seal Taxa (Carnivora, Phocidae) From The North Sea Basin, Vestnik Zoologii 48 (5), pp. 419-432 : 424-426

Gryphoca nordica Koretsky, Rahmat et Peters , sp. n. (рl. 2, 2A–2D, 3A–3D; table 2)

H o l o t y p e. Incomplete right humerus MAB 4602 (pl. 2, 2A–2D), Oertijdmuseum de Groene Poort , Boxtel, The Netherlands.

P a r a t y p e s. From the type locality: R. humerus (distal half) MAB 4604 ; L. humerus (distal half) MAB 4700 ; L. humerus (proximal half) MAB 460 . All in Oertijdmuseum de Groene Poort , Boxtel (51.61°36' N, 5.32°19' E) .

From Gram, claypit of Gram Teglvaerk, Jutland, Denmark, marine Gram Formation: R. humerus MSM 1404x1 (pl. 2, 3A–3D); L. femur (distal part) MSM 1004x1; both in MidtsØnderjyllands Museum, Gram Slot, Denmark.

T y p e l o c a l i t y. Underwater sandpit “de Kuilen”, Mill-Langenboom, province of Noord Brabant, The Netherlands, late Miocene — early Pliocene.

S t r a t i g r a p h i c a l r a n g e. Late Miocene — early Pliocene of Mill-Langenboom, The Netherlands ( Wijnker et al., 2008) and late Miocene (early–middle Tortonian, 8.0– 11.5 ma) of Gram, Jutland, Denmark ( Hansen, Hansen, 2003).

E t y m o l o g y. After n o r d (Danish: noun, neuter) = the North, Latinized to n o r d i c a (adj.) = from the North, referring to the northern part of Europe.

D i a g n o s i s. Deltoid crest of humerus with ventral border very sharp and sculptured, overhanging deep spiral groove; lesser tubercle flattened, rectangular, deviates almost 45° from bone’s axis; head compressed in cranio-caudal direction; ratio of head width / head height — 97 %.

D e s c r i p t i o n a n d c o m p a r i s o n. Postcranial elements of Gryphoca nordica belong to a medium-sized representative of Phocinae , equivalent in size to Recent Histriophoca fasciata . Morphological characters similar to Gryphoca similis (pl. 2, 2A–2D) are: the deltoid crest is strongly developed, with its maximum width in its proximal part at the level of the lesser tubercle. The deltoid tuberosity is weakly developed, but clearly seen on the proximal part of the deltoid crest. The intertubercular groove is narrow and deep. The ventral border of the deltoid crest is very sharp and sculptured, overhanging as an anconeal crest (ac, pl. 2, 1D). The radial groove (= musculospiral groove) is strongly developed (sg, pl. 2, 1D).

The new species G. nordica differs from Gryphoca similis by its smaller size. In addition, the head of the humerus is compressed in the cranio-caudal direction, not round in shape. The proximal part of the deltoid crest is located at the same level as the lesser tubercle and slightly above the head. The lesser tubercle resembles a flattened rectangle, deviates almost 45° from the bone’s axis, and is situated slightly above the head, but higher than the greater tubercle.

The supracondylar fossa of the femur, located above the lateral condyle, is easily visible. The patellar surface is very pronounced, sharp and has a prominent outlinesculptural compared to the bone’s overall surface.

D i s c u s s i o n. The rare genus Gryphoca was introduced by Van Beneden (1877) based on material from the Antwerp area, Belgium. Although the genus is known to researchers by name, it appears that no one except Ray (1976) has re-examined the original material critically. Koretsky and Ray (2008) re-evaluated, described and compared West European and North American material, and proposed a diagnosis for the genus Gryphoca . In this study, we assign a new, smaller species, G. nordica , to the genus Gryphoca on the basis of only a few fragmentary and rolled bones (but with very distinctive morphological features) from the late Miocene of Northern and Western Europe.

Because none of the specimens in the Denmark collection is complete, we choose the humerus from The Netherlands (with the same geological age, better preservation, and apparently the same morphology; see pl. 2, 2A–2D, and table 2) as the best available holotype.

The fragmentary remains, as well as the lack of further postcranial elements, may raise some doubts about their assignment to the genus Gryphoca . However, the preserved material (four humeri and a femur) and previous publications based on the Western European and eastern United States material ( Beneden, 1877; Koretsky, Ray, 2008), allow, with a high degree of probability, assignment of this seal to the genus Gryphoca and the introduction of a new taxon of specific rank. We think this approach is more justified than establishment of a new taxon of generic rank.

Furthermore, according to the ecomorphotype hypothesis of Koretsky (2001), these bones belong to the same group (ecomorphotype V) on the basis of characters such as: lesser tubercle slightly higher than or at same level as the head of the humerus, and deviates from the bone’s axis; intertubercular groove narrow; maximum width of the deltoid crest located in its proximal part. Ecomorphological analysis is here applied on the level of alpha systematics.

Figures

Plate 1. Fig. 1. Pontophoca sarmatica, right femur; Kishinev, Moldavia (Middle Miocene, middle Sarmatian); аfter Koretsky, Grigorescu (2002: fig. 3); USNM 214980: 1A — cranial; 1B — caudal view. Рис. 1. Pontophoca sarmatica, правая бедренная кость; Кишинев, Молдова (средний миоцен, средний сармат); по: Koretsky, Grigorescu (2002: рис. 3); USNM 214980: 1A — вид спереди; 1B — вид сзади.