A Cormorant from the Late Oligocene of Enspel, Germany (Aves, Pelecaniformes, Phalacrocoracidae)

329

I Senckenbergiana lethaea r 81 I (2~ 1 329-3331 3~ext-figs I Frankfurt am Main, 28.12.2001 I

A cormorant from the late Oligocene of Enspel, Germany (Aves, Pelecaniformes, Phalacrocoracidae)

With 3 Text-figures

GERALD MAYR

Abstract

A foot of a cormorant (Aves, Pelecaniformes, Phalacrocoracidae) is described from the Late Oligocene of the locality Enspel near Bad Marienberg, Germany (MP 28). The specimen is tentatively assigned to the genus Oligocorax LAMBRECHT 1933 which is shown to be morphologically distinct from the Recent genus Phalacrocorax. The find from Enspel is the earliest fossil record of the Phalacrocoracidae described so far. K e y w o r d s : Enspel, late Oligocene, Aves, Pelecaniformes, Phalacrocoracidae.

Kurzfassung

[Ein Kormoran aus dem sp~iten Oligoz~in von Enspel, Deutschland (Aves, Pelecaniformes, Phalacrocoracidae).] -- Ein Fug eines Kormorans (Aves: Pelecaniformes: Phalacrocoracidae) wird aus dem sp~iten Oligozfin (MP 28) von Enspel bei Bad Marienberg, Deutschland, beschrieben. Das Exemplar wird unter Vorbehalt zur Gattung Oligocorax LAMBRECHT 1933 gestellt, deren morphologische Unterschiede zur rezenten Gattung Phalacrocorax dargestellt werden. Bei dem Fund aus Enspel handelt es sich um den ~iltesten bisher beschriebenen Nachweis der Phalacrocoracidae.

Introduction

According to ORTA (1992), cormorants (Pelecaniformes: The fossil record of cormorants was summarized by BROD- Phalacrocoracidae) comprise 39 recent species ofpiscivorous KORB (1963), CHENEVAL (1984), and OLSON (1985). MOURER- birds which are classified in a single genus, Phalacrocorax. CHAUVlR• (1982) listed the Phalacrocoracidae in the Upper Cormorants are aquatic birds which occur both in marine and Eocene to Upper Oligocene avifauna of the Quercy (France), freshwater environments, such as coastal waters, lakes, open but the so far earliest described fossil specimens are from the swamps, and slow-flowing rivers. Today, cormorants have a early Miocene of Europe and North America. Three species worldwide distribution but are most diversified on the South- were reported from the early Miocene of France: Phalacroc- ern Hemisphere; most species live in tropical or temperate orax intermedius (MILNE-EDWARDS 1867), Phalacrocorax waters. There is general agreement, that the Phalacrocoraci- littoralis (MILNE-EDWARDS 1863), and Phalacrocorax miocae- dae are the sister taxon of the Anhingidae (darters) (e. g. nus (MILNE-EDWARDS 1867). Together with two North Ameri- SIEGEL-CAUSEY 1988). can species, P littoralis and P miocaenus were assigned to the

Address of the author: Dr. GERALD MAYR, Forschungsinstitut Senckenberg, Sektion Ornithologie, Senckenberganlage 25; D-60325 Frankfurt am Main. - E-mail: [email protected] 330 MAYR: A cormorant from the late Oligocene of Enspel, Germany (Aves, Pelecaniformes, Phalacrocoracidae) new genus Oligocorax by LAMBRECHT (1933), the type of according to CHENEVAL (1984), however, those described by which is P. littoralis (see BRODKORB 1952). However, con- MARTINI (1974) actually belong to Nectornis miocaenus. cerning the North American taxa, WETMORE (1935) consid- Phalacrocorax marinavis was described by SHUFELDT ered generic separation from the recent genus Phalacrocorax (1915) from the lower Miocene of Oregon, and is known unjustified, and although he did not comment on the generic from a few isolated skeletal elements including a fragmentary status of the French species, these were subsequently also tarsometatarsus. "Phalacrocorax" subvolans BRODKORB classified within the genus Phalacrocorax by most authors 1956, also from the lower Miocene of North America, was (e. g. BRODKORB 1963, PAICHELER et al. 1978). CHENEVAL assigned to the Anhingidae by BECKER (1986) and is the ear- (1984) maintained this generic allocation for "Phalacroc- liest fossil record of this family (see ALVARENGA 1995 and orax" littoralis but classified "Phalacrocorax" miocaenus CAMPBELL 1996 for a review of other fossil Anhingidae). into the new genus Nectornis. I consider classification of Presented in this study is a record of the Phalacrocoracidae "Phalacrocorax" littoralis into the genus Oligocorax LAM- from the locality En@el near Bad Ma¡ Germany. The BRECHT 1933 to be justified, morphological differences be- site is a lake deposit which o¡ in the Late Oligocene (see tween the genera Oligocorax and Phalacrocorax are listed in FELDER et al. 1998 and PIRRUNG 1998 conceming the geology of the discussion below. the site). According to SrORCH et al. (1996), the deposits of LAMBRECHT (1933) and MARTINI (1974) reported remains Enspel belong to the stratigraphic unir MP 28 and thus have an of Oligocorax littoralis from the early Miocene of Germany, absolute age of about 25 million years (LEGENDRE & L• 1997). Since 1991, annual excavation campaigns have yielded a large number of fossil plants, invertebrates and verte- brates. The specimen is the first identi- fiable bird remain from the locality. The anatomical terminology fol- lows BAUMEL & WITMER(1993); com- parisons were made with the follow- ing species of recent Phalacrocoraci- dae (all in the collection of Forsc- hungsinstitut Senckenberg): Phalacro- eorax aristotelis, Ph. auritus, Ph. car- bo, Ph. gaimardi, and Ph. harrisi.

Systematics

Pelecaniformes SHARPE 1891

Phalacrocoracidae BONAPARTE 1854

? Oligocorax LAMBRECHT 1933 sp.

Referred specimen: PW 5000a+b (right foot and distal end of right tibiotarsus on two slabs, text-figs 1, 2), currently de- posited in the Landesamt fª Denkmalp- flege Rheinland-Pfalz, Mainz (the specimen will later be transferred to the Naturhisto- risches Museum Mainz, Germany).

Locality and horizon: Enspel near Bad Marienberg in the Westerwald, Rheinland-Pfalz, Germany; Late Oligocene, MP 28 (STORCHet al. 1996).

Text-fig. 1. ? Oligocorax LAMBRECHT1933 sp., right foot (specimen PW 5000a). Coated with ammonium chloride to enhance contrast. Scale bar equals 10 mm. MAYR: A cormorant from the late Oligocene of Enspel, Germany (Aves, Pelecaniformes, Phalacrocoracidae) 331

D i m e n s i o n s (in millimeters): Tarsometatarsus: estimated teology, it is likely that the feet of the cormorant from Enspel length, ~48; distal width, ~ 10. Pedal phalanges: di pl, 18.0; di p2, were webbed like in recent Phalacrocoracidae. 8.3; dII pl, 19.1; dll p2, 14.1; dII p3, 6.5; dtIl pl, 17.8; dIII p2, 15.7; dIII p3, 12.8; dIII p4, 8.5; dlV pl, 20.0; dIV p2, 15.9z dIV p3, 13.1; dlV p4, 12.9; dlV p5, 8.1. Discussion Description and comparison The specimen presented in this study is the earliest certain Only the medial side of the condylus medialis is visible. In its record of the Phalacrocoracidae described so far. Although it shape it agrees with the condylus medialis of Oligocorax closely resembles recent cormorants in foot morphology, sev- littoralis as figured by MJLNE-EDWARDS (1867-71: pl. 42 eral differences in the morphology of the distal tibiotarsus fig. 11). Like in the latter, it is narrower in proximo-distal and the tarsometatarsus (see description and below), suggest direction than the condylus medialis of the recent genus that it does not belong to the genus Phalacrocorax. Phalacrocorax. The cormorant from Enspel is larger than Nectornis mio- The tarsometatarsus is broken in its middle and whereas caenus, the estimated length of the tarsometatarsus is about the distal hall of the bone is seen in dorso-ventral view, its 48 mm vs. 38.8-41.5 mm in N. miocaenus (the measurements proximal half is exposed in medio-lateral view. In its propor- are taken from CHENEVAL 1984). No complete tarsometatar- tions, the bone resembles the tarsometatarsus of other Phalac- sus is known from Oligocorax littoralis, but the proximal end rocoracidae, whereas that of the Anh- ingidae is much shorter and stouter. Like in recent Phalacrocoracidae, there is a sesamoid bone at the tarsal joint. The crista medialis hypotarsi is less protruding than in recent cormorants; apart from being proximo-distally somewhat shorter, it has a similar shape to that of Oligoeorax littoralis as figured by MILNE-EDWARDS(1867- 71: pl, 42 fig. 7). The distal margin of the crista medialis hypotarsi is per- pendicular to the longitudinal axis of the tarsometatarsus, whereas it is passing at a less acute angle into the shaft in Phalacrocorax. The distal end of the bone differs from that of recent Phalacrocoracidae and resembles Nec- tornis miocaenus in that the trochlea metatarsi II reaches as far distally as the trochlea metatarsi III (in recent cormorants it is shorter). Like in recent cormorants, the pedal phalanges are dorso-ventrally flattened, and the fourth toe distinctly exceeds the third in length (the ap- proximate length of the three anterior roes, from the second to the fourth, is -38, ~55, ~68). The claws are very straight, the tuberculum extensorium is hardly protruding and the part of the phalanx proximally adjacent to it fairly long. Given the great similarity in os-

Text-fig. 2. ? Oligocorax LAMBRECHT1933 sp., right foot (specimen PW 5000b). The arrow indicates the sesamoid bone at the tarsal joint. Coated with ammonium chloride to enhance contrast. Scale bar equals 10 mm. 332 MAYR: A cormorant from the late Oligocene of Enspel, Germany (Aves, Pelecaniformes, Phalacrocoracidae)

morant from Enspel is also distinguished from recent Phalac- rocoracidae. Judging from the illustrations in MILNE-EDWARDS (1867- 4" 71), the crista medialis hypotarsi of Nectornis protrudes more strongly than in Oligocorax littoralis and the cormorant from Enspel. As mentioned above, the latter agrees with Nectornis and differs from recent Phalacrocorax in that the trochlea metatarsi II reaches as far distally as the trochlea metatarsi III. The Text-fig. 3. Proximal end of tarsometatarsus (A, B) and condylus distal end of the tarsometatarsus of Oligocorax littoralis is medialis of tibiotarsus (C, D) in comparison. A, C) Oligoeorax unknown so far, but a far distally reaching trochlea metatarsi li littoralis (MmNE-EDWARDS 1863) (after MILNE-EDWARDS 1867-71); is also found in the Anhingidae which indicates that this condi- B, D) Phalacrocorax aristotelis LINNAEUS 1761. The arrows indicate the different shape of the crista medialis hypotarsi (A, B) and of the tion might be plesiomorphic within the Phalacrocoracidae. condylus medialis (C, D). Slighdy schematie and not to scale. The tentative assignment of the Enspel cormorant to the genus Oligocorax might be confirmed or refuted by future discovery of better preserved specimens. of this bone figured by MILNE-EDWARDS (1867-71) and CHE- The presence of cormorants in the deposits of Enspel NEVAL (1984) is of comparable size to that of the Enspel indicates that Phalacrocoracidae and Anhingidae diverged cormorant. well before the Late Oligocene. Concerning the distal end of the tibiotarsus and the proximal end of the tarsometatarsus, the genus Oligocorax differs from Phalacrocorax in: (l) condylus medialis of tibiotarsus Acknowledgements narrower in proximo-distat direction; (2) crista medialis hypotarsi less strongly protruding plantarly, with (3) medio-lat- I thank M. WUTTKE (Landesamt fª Denkmalpflege Rhein- erally narrower plantar margin, and (4) distal margin perpen- land-Pfalz, Mainz) for the loan of the fossil specimen and for dicular to the longitudinal axis of the tarsometatarsus (in bibliographic help, and A. HESSE (Museum f'ª Naturkunde Phalacrocorax it is passing ata less acute angle into the und Vorgeschichte, Dessau) for passing ir to me; S. TRANK- shafl) (text-fig. 3). In all of these features, which might be NER (Forschungsinstimt Senckenberg, Frankfurt am Main) plesiomorphic within the Phalacrocoracidae, the fossil cor- took the photographs.

References

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Manuscript submitted: 2001-03-30; accepted: 2001-05-30.