Byzantinia de Bruijn, 1976

Sen, Sevket, 2016, Rodents, lagomorphs and insectivores, Geodiversitas 38 (2), pp. 299-314 : 300-301

Genus Byzantinia de Bruijn, 1976

TYPE SPECIES. — Byzantinia pikermiensis de Bruijn, 1976 .

Byzantinia bayraktepensis Ünay, 1980 ( Fig. 1 A-E)

TYPE LOCALITY. — Bayraktepe 1, Turkey, MN8.

MATERIAL. — From Küçükçekmece West: right M1 (3.32 × 2.19), fragment of left maxillary with M2 (2.33 × 1.59) and M3 (1.76 × 1.36), distal part of a right m1 (– × 1.79), right m2 (2.69 × 1.88) and left m2 (2.43 × 1.76). Specimens numbered as MNHN.F.TRQ955 to TRQ959.

DESCRIPTION

All the molars are rather high-crowned, the lophs are thick and the ridges connecting the cusps are as high as the cusps. On the M1, the anterocone is deeply split into two cusps of similar volume. The labial anterocone has a thick spur connected to the base of the paracone, while the lingual one has a bulge on its lingual side. The sinus is directed distally. The ectoloph between the paracone and metacone is complete. This tooth has four roots, one mesial, one lingual and two distal.

The M2 is elongated and tapers distally. The protosinus is a wide depression delimited mesially by a low lingual anteroloph. The labial anteroloph is strong and fused to the base of the paracone. The sinus is very oblique distally. There are four roots.

The M3 is similar to M 2 in its general pattern, but with distal part notably reduced, in particular the hypocone and posteroloph. The sinus is directed distally, but is considerably reduced compared to that of M2. The M3 has three roots.

The preserved distal part of an m1 displays a strait sinusid directed forward and delimited by a thick cingulum. The posterolophid is cusp shaped.

The occlusal outline of the m2 is rather quadrangular. The anterosinusid is a shallow depression, while the protosinusid is deep due to the fact that the labial anterolophid is well developed. The mesolophid is a thick spur directed toward the metaconid. The sinusid is directed mesially. A thick cingulum runs along the labial face of the tooth. The posterolophid is cusp shaped. This tooth has three roots, one strong mesial and two small distal roots.

COMPARISON

The material described here above is rather homogenous in morphology and size, and therefore securely referred to the same species. It is important to clarify this aspect, because many late Miocene localities in Turkey and Greece yielded two species of Byzantinia . The subfamily Cricetodontinae is well documented in Turkey and in the Balkan countries since the early Miocene. Among several genera referred to this group, the specimens from Küçükçekmece fit with the genus Byzantinia in having rather high crowned molars with strong lophs between the cusps, well-divided anterocone on M1, and distally elongated M2 and M3. This genus is known by eleven species in this region during the latest middle Miocene and late Miocene. The middle Miocene species B. cariensis (Sen & Ünay, 1979) and B. eskihisarensis (Tobien, 1978) , as well as two late Miocene species B. nikosi de Bruijn, 1976 and B. ozansoyi Ünay, 1980 have molars smaller than the Küçükçekmece sample, and these species have a “funnel” structure on M1 and M2, which is absent on the M1 and M2 from Küçükçekmece. This funnel is formed by the connection of the protoloph, ectoloph, mesoloph and endoloph, it is apparently a character inherited from the ancestral genus Cricetodon . Byzantinia unayae Rummel, 1998 from Karaözü (Sivas Basin, Turkey, MN10-11) is similar in size, but different in morphology from the Küçükçekmece species. Its M1 has lingual spurs of the anterocone and protocone, its M2 and M3 have labial anteroloph rather strait and not connected to the paracone, its M3 is not reduced distally, and the m2 and m3 taper mesially. Although not illustrated laterally, the description given by Rummel (1998) shows that the molars of this species are higher crowned than those of Küçükçekmece. Another group of Byzantinia , including the species B. dardanellensis Ünay, 1980 , B. hellenicus (Freudenthal, 1970) and

B. pikermiensis de Bruijn, 1976 , is characterized with high crowned and lophodont molars, and lack of the funnel on M1 and M2. The cusps of both upper and lower molars are included in the lophs, the lophs are as high as the cusps, and the first and particularly the second molars are elongated. All these characters are not seen on the Küçükçekmece specimens.

The size and morphology of the Küçükçekmece specimens fit better with B. bayraktepensis Ünay, 1980 . This species was initially described from Bayraktepe-1, a locality situated to the southeast of the Dardanelles Strait, and dated as latest middle Miocene because of the absence of murids in the fauna and the occurrence of Anchitherium and Listriodon in nearby horizons ( Ünay 1980, 1981). Later on Rummel (1998) referred to this species the specimens from the localities of Dereikebir (Edirne, Thrace), Mahmutköy, Pişmanköy (Thrace) and Yenieskihisar (Muğla, SW Turkey). All these localities are correlated to MN8 or MN9, i.e. across the middle-late Miocene boundary. The material from Sinap Loc. 1 described by Sen (1990) as B. cf. dardanellensis can also be included in this species.Magnetostratigraphy of the Sinap Formation dated this locality to 9.68 Ma ( Kappelman et al. 2003). Lately Joniak & de Bruijn (2015) attributed to this species the well-preserved material from the locality of Tuğlu 19 in the Çankiri Basin, central Anatolia. This locality is correlated to MN9 based on palaeontological and magnetostratigraphic data ( Mazzini et al. 2013; Joniak & de Bruijn 2015).

Byzantinia orientalis ( Lungu, 1981) from Buzhor- 1 in Moldova could be a synonym of B. bayraktepensis . Its molars do not display any reliable morphological difference from those of B. bayraktepensis from its type locality Bayraktepe-1, although the size of molars as given by Lungu (1981) is either identical or larger than that of the type material. New measurements of the cricetodontine molars from Buzhor-1 are necessary for a reliable size comparison.

Figures

FIG. 1. — Byzantinia bayraktepensis from Küçükçekmece West, Turkey: A, M1 dext (MNHN.F.TRQ955); B, M2-3 sin (TRQ956); C, fragment of m1 dext (TRQ957); D, m2 dext (TRQ958); E, m2 sin (TRQ959). Spalacidae gen. and sp. indet. from Küçükçekmece: F, M2 sin (TRQ951); G, m3 sin (TRQ952). Scale bar: 1 mm.