I Senckenbergiana lethaea
r 81 I (2~ 1 329-3331 3~ext-figs I
329
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.
K u r z f a s s u n g
[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:
Phalacrocoracidae) comprise 39 recent species o f p i s c i v o r o u s birds which are classified in a single genus, Phalacrocorax.
Cormorants are aquatic birds which occur both in m a r i n e and freshwater environments, such as coastal waters, lakes, open swamps, and slow-flowing rivers. Today, cormorants have a worldwide distribution but are most diversified on the South- ern Hemisphere; most species live in tropical or temperate waters. There is general agreement, that the Phalacrocoraci- dae are the sister taxon o f the Anhingidae (darters) (e. g.
SIEGEL-CAUSEY 1988).
The fossil record o f cormorants was summarized by BROD- KORB (1963), CHENEVAL (1984), and OLSON (1985). MOURER- CHAUVlR• (1982) listed the Phalacrocoracidae in the Upper Eocene to Upper Oligocene avifauna o f the Quercy (France), but the so far earliest described fossil specimens are from the early Miocene o f Europe and North America. Three species were reported from the early Miocene o f France: Phalacroc- orax intermedius (MILNE-EDWARDS 1867), Phalacrocorax littoralis (MILNE-EDWARDS 1863), and Phalacrocorax miocae- nus (MILNE-EDWARDS 1867). Together with two North Ameri- 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: gmayr@sng.uni-frankfurt.de
330 MAYR: A cormorant from the late Oligocene of Enspel, Germany (Aves, Pelecaniformes, Phalacrocoracidae)
new genus Oligocorax by LAMBRECHT (1933), the type of which is P. littoralis (see BRODKORB 1952). However, con- cerning the North American taxa, WETMORE (1935) consid- ered generic separation from the recent genus Phalacrocorax unjustified, and although he did not comment on the generic status of the French species, these were subsequently also classified within the genus Phalacrocorax by most authors (e. g. BRODKORB 1963, PAICHELER et al. 1978). CHENEVAL (1984) maintained this generic allocation for "Phalacroc- orax" littoralis but classified "Phalacrocorax" miocaenus into the new genus Nectornis. I consider classification of
"Phalacrocorax" littoralis into the genus Oligocorax LAM- BRECHT 1933 to be justified, morphological differences be- tween the genera Oligocorax and Phalacrocorax are listed in the discussion below.
LAMBRECHT (1933) and MARTINI (1974) reported remains of Oligocorax littoralis from the early Miocene of Germany,
according to CHENEVAL (1984), however, those described by MARTINI (1974) actually belong to Nectornis miocaenus.
Phalacrocorax marinavis was described by SHUFELDT (1915) from the lower Miocene of Oregon, and is known from a few isolated skeletal elements including a fragmentary tarsometatarsus. "Phalacrocorax" subvolans BRODKORB
1956, also from the lower Miocene of North America, was assigned to the Anhingidae by BECKER (1986) and is the ear- liest fossil record of this family (see ALVARENGA 1995 and CAMPBELL 1996 for a review of other fossil Anhingidae).
Presented in this study is a record of the Phalacrocoracidae from the locality En@el near Bad Ma¡ Germany. The site is a lake deposit which o¡ in the Late Oligocene (see FELDER et al. 1998 and PIRRUNG 1998 conceming the geology of the site). According to SrORCH et al. (1996), the deposits of Enspel belong to the stratigraphic unir MP 28 and thus have an 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
P e l e c a n i f o r m e s SHARPE 1891 P h a l a c r o c o r a c i d a e BONAPARTE 1854
? Oligocorax LAMBRECHT 1933 sp.
R e f e r r e d s p e c i m e n : 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).
L o c a l i t y a n d h o r i z o n : Enspel near Bad Marienberg in the Westerwald, Rheinland-Pfalz, Germany; Late Oligocene, MP 28 (STORCH et al. 1996).
Text-fig. 1. ? Oligocorax LAMBRECHT 1933 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 length, ~48; distal width, ~ 10. Pedal phalanges: di pl, 18.0; di p2, 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.
D e s c r i p t i o n a n d c o m p a r i s o n
Only the medial side of the condylus medialis is visible. In its shape it agrees with the condylus medialis of Oligocorax littoralis as figured by MJLNE-EDWARDS (1867-71: pl. 42 fig. 11). Like in the latter, it is narrower in proximo-distal direction than the condylus medialis of the recent genus Phalacrocorax.
The tarsometatarsus is broken in its middle and whereas the distal hall of the bone is seen in dorso-ventral view, its proximal half is exposed in medio-lateral view. In its propor- tions, the bone resembles the tarsometatarsus of other Phalac- rocoracidae, whereas that o f 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 cormo- rants; apart from being proximo-dis- tally 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 o f 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 o f 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 LAMBRECHT 1933 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.
teology, it is likely that the feet of the cormorant from Enspel were webbed like in recent Phalacrocoracidae.
Discussion
The specimen presented in this study is the earliest certain record of the Phalacrocoracidae described so far. Although it closely resembles recent cormorants in foot morphology, sev- eral differences in the morphology of the distal tibiotarsus and the tarsometatarsus (see description and below), suggest that it does not belong to the genus Phalacrocorax.
The cormorant from Enspel is larger than Nectornis mio- caenus, the estimated length of the tarsometatarsus is about 48 mm vs. 38.8-41.5 mm in N. miocaenus (the measurements are taken from CHENEVAL 1984). No complete tarsometatar- sus is known from Oligocorax littoralis, but the proximal end
332 MAYR: A cormorant from the late Oligocene of Enspel, Germany (Aves, Pelecaniformes, Phalacrocoracidae)
4"
Text-fig. 3. Proximal end of tarsometatarsus (A, B) and condylus medialis of tibiotarsus (C, D) in comparison. A, C) Oligoeorax littoralis (MmNE-EDWARDS 1863) (after MILNE-EDWARDS 1867-71);
B, D) Phalacrocorax aristotelis LINNAEUS 1761. The arrows indicate the different shape of the crista medialis hypotarsi (A, B) and of the condylus medialis (C, D). Slighdy schematie and not to scale.
o f this bone figured by MILNE-EDWARDS (1867-71) and CHE- NEVAL (1984) is o f comparable size to that o f the Enspel cormorant.
Concerning the distal end o f the tibiotarsus and the proxi- mal end o f the tarsometatarsus, the genus Oligocorax differs from Phalacrocorax in: ( l ) condylus medialis o f tibiotarsus narrower in proximo-distat direction; (2) crista medialis hy- potarsi less strongly protruding plantarly, with (3) medio-lat- erally narrower plantar margin, and (4) distal margin perpen- dicular to the longitudinal axis o f the tarsometatarsus (in Phalacrocorax it is passing a t a less acute angle into the shafl) (text-fig. 3). In all o f these features, which might be plesiomorphic within the Phalacrocoracidae, the fossil cor-
m o r a n t from Enspel is also distinguished from recent Phalac- rocoracidae.
Judging from the illustrations in MILNE-EDWARDS (1867- 71), the crista medialis hypotarsi o f 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 met- atarsi II reaches as far distally as the trochlea metatarsi III. The distal end o f the tarsometatarsus o f Oligocorax littoralis is u n k n o w n so far, but a far distally reaching trochlea metatarsi li is also found in the Anhingidae which indicates that this condi- tion might be plesiomorphic within the Phalacrocoracidae.
The tentative assignment o f the Enspel cormorant to the genus Oligocorax might be c o n f i r m e d or refuted by future discovery o f better preserved specimens.
The presence o f cormorants in the deposits o f Enspel indicates that Phalacrocoracidae and Anhingidae diverged well before the Late Oligocene.
Acknowledgements
I t h a n k M. WUTTKE (Landesamt fª Denkmalpflege Rhein- land-Pfalz, Mainz) for the loan o f the fossil specimen and for bibliographic help, and A. HESSE (Museum f'ª Naturkunde und Vorgeschichte, Dessau) for passing ir to me; S. TRANK- NER (Forschungsinstimt Senckenberg, Frankfurt am Main) took the photographs.
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M a n u s c r i p t submitted: 2001-03-30; accepted: 2001-05-30.
