Thomas Mörs

Aspects of diversity in early Antarctic penguins

Penguin bones from the Eocene La Meseta Formation (Seymour Island, Antarctic Peninsula) constitute the only extensive fossil record of Antarctic Sphenisciformes. Here, we synonymize some of the recognized genera (Anthropornis with Orthopteryx, Delphinornis with Ichtyopteryx) and species (Anthropornis nordenskjoeldi with Orthopteryx gigas, Delphinornis gracilis with Ichtyopteryx gracilis). Moreover, we suggest that Antarctic species of Anthropornis and Palaeeudyptes, so-called giant penguins, may in fact comprise only one species each instead of two, based on evidence of well-marked sexual dimorphism. We also present new estimates of body mass based on femora testifying to the impressive scope of interspecific body-size variation in Eocene Antarctic penguins.

Die erste Wirbeltierfauna aus der miozänen Braunkohle der Niederrheinischen Bucht (Ville-Schichten, Tagebau Hambach)

This paper describes the first Miocene vertebrate fauna from the Ville Series of the Lower Rhine Embayment in western Germany. The fossil material was discovered in the vast Hambach open cast lignite mine ofRheinbraun. The numerous remains, mostly isolated teeth and disarticulated bones, were accumulated in a channel-fill within the main lignite seam. The fauna consists of chondrichthyans, teleosteans, amphibians, reptiles, and mammals which inhabited brackish-estuarine, lacustrine-fluviatile, and terrestrial environments.This is the first fauna to provide an insight into the diversity of vertebrates which lived in the forested peat swamps of the Rhenish Tertiary. Based on the rich association of more than 70 mammalian taxa, including about 30 rodent species, this late Orleanian fauna can be correlated with the upper part of the Mammalian Neogene biozone MN 5. Therefore the middle part of the main lignite seam (horizon 6C of the local lithostratigraphy) can be placed in the early middle Miocene. This means an age of 15.2-16.0 Ma (Langhian or Reinbekian of the stratigraphy of the NW German Tertiary).For some mammalian taxa (Lanthanotherium, Plesiosorex,Miopetaurista, Myoglis, Fahlbuschia, ‘Lartetomys’, Anchitheriomys, Dorcatherium), Hambach 6C is one of the richest European localities. In addition this assemblage contains some very rare mammals (‘Lartetomys’, Anchitheriomys, Orygotherium, Pliopithecus). The Hambach vertebrates are of great palaeobiogeographic importance as they represent the north westernmost outpost of terrestrial Miocene faunas in Europe.KurzfassungDie hier vorgestellte Vertebratenfauna aus den miozänen Ville-Schichten der Niederrheinischen Bucht gibt erstmals einen Einblick in den Artenreichtum der Tierwelt in den Braunkohle-Sumpfwäldern des rheinischen Tertiärs. Die zahlreichen zusammengeschwemmten, disartikulierten Reste, vor allem Zähne und Knochen, stammen aus einer in das Rheinische Hauptflöz eingeschnittenen Flußrinne im Tagebau Hambach derRheinbraun AG. Die Fauna umfaßt Fische, Amphibien, Reptilien und Säugetiere aus brackisch-ästuarinen, limnisch-fluviatilen und terrestrischen Habitaten.Die mit über 70 Spezies, darunter ca. 30 Nagetierarten, sehr reiche Mammalierassoziation repräsentiert eine spätorleanische Fauna, die in den oberen Teil der Säugerzone MN 5 eingestuft wird. Damit kann für den mittleren Abschnitt des Hauptflözes (Schicht 6C) erstmals ein biostratigraphisch begründetes, frühmittelmiozänes Bildungsalter von ca. 15.2-16.0 Ma (Langh bzw. Reinbek nach der NW-deutschen Tertiär-Gliederung) angegeben werden.Für einige Mammalier (Lanthanotherium, Plesiosorex,Miopetaurista, Myoglis, Fahlbuschia, ‘Lartetomys’, Anchitheriomys, Dorcatherium) ist Hambach 6C eines der reichsten Vorkommen. Der Nachweis von sonst z.T. extrem seltenen Säugertaxa (‘Lartetomys’, Anchitheriomys, Orygotherium, Pliopithecus) ist auch paläobiogeographisch von Bedeutung, da es sich um die nordwestlichste Fundstelle im terrestrischen Miozän Europas handelt.

First Record Of Soft-Shelled Turtles (Cryptodira, Trionychidae) From The Late Cretaceous Of Europe

ABSTRACT Fossil soft-shelled turtles (Trionychidae) have so far been recognized in all continents except Antarctica, based largely on remains preserving their diagnostic sculptured shell bones. The origin of the group is generally assumed to be in the Early Cretaceous of Asia, whereas they first appear in North America and Europe during the Late Cretaceous and Paleocene, respectively. Here we describe the first record of an indeterminate trionychid from the late early Campanian from southern Sweden, a part of the paleobiogeographically isolated Fenno-Scandian Shield, thus extending the stratigraphic record of the group in Europe back about 15 Ma into the Late Cretaceous. Our finding provides evidence against the currently favored dispersal scenario in which trionychid turtles are interpreted to have come to Europe first during the Paleocene either directly from North America or via Asia. The described indeterminate trionychid possibly represents a relic of a pre-Cretaceous endemic radiation of North European trionychids living mainly on the Fenno-Skandian Shield or it may indicate a potential lower latitude dispersal route of trionychids from Asia to North America via Europe during the Late Cretaceous.

The enamel microstructure ofAnchitheriomys (Rodentia, Mammalia) in comparison with that of other beavers and of porcupines

KurzfassungIn der Zahnschmelz-Mikrostruktur der Inzisiven lassen sich die Hystricidae (Stachelschweine) mit ihren multiserialen Hunter-Schreger-Bändern (HSB) gut von den Castoridae (Biber) unterscheiden, die grundsätzlich uniseriale HSB besitzen. Allerdings ist der Zahnschmelz der Biber nicht einheitlich aufgebaut. WährendPalaeocastor, Steneofiber undCastor recht typische uniseriale HSB besitzen, die nur beiCastor etwas miteinander verschmelzen, tritt diese Verschmelzung der HSB in der Gruppe umTrogontherium undCastoroides sehr regelmäßig und verstärkt auf.Anchitheriomys zeigt das Schmelzmuster dieser zweiten Bibergruppe. Daraus folgt nicht nur, daßAnchitheriomys ohne Zweifel ein Biber ist, sondern gleichzeitig, daß sich mindestens zwei Gruppen innerhalb der Biber am Schmelzmuster der Inzisiven unterscheiden lassen. Damit kann das Schmelzmuster als wichtiges Kriterium für die systematische Gliederung der Familie verwendet werden.Im Schmelzmuster der Backenzähne konnten ebenfalls Unterschiede zwischen Stachelschweinen und Bibern gefunden werden. Auch hier paßtAnchitheriomys mit einem ausgeprägten inneren radialen Schmelz in einem zweischichtigen Schmelzmuster bestens zu den Bibern. Bei den Stachelschweinen wird der Schmelz in der ganzen Dicke von dicken HSB durchzogen. Anhand des Schmelzmusters können demnach auch isolierte Backenzähne entweder den Bibern oder den Stachelschweinen zugeordnet werden, wenn die Zahnmorphologie nicht ausreicht.AbstractIn the enamel microstructure of the incisors, porcupines (Hystricidae) are characterized by multiserial Hunter-Schreger bands (HSB) while beavers (Castoridae) basically have uniserial HSB. In addition, two groups can be differentiated among beavers based on enamel microstructure.Palaeocastor, Steneofiber andCastor show rather typical uniserial HSB. OnlyCastor shows a slight tendency of fusion of the bands. In contrast,Trogontherium andCastoroides are characterized by the regular occurrence of fused bands.Anchitheriomys, having uniserial HSB and a high frequency of fused bands fits well with theTrogontherium group, proving the castorid nature ofAnchitheriomys. Furthermore, the enamel differentiation observed among the Castoridae thus provides an important character for further systematic subdivision of the beavers.In the enamel of the cheek teeth, porcupines can be told apart from beavers as well.Anchitheriomys shows a two-layered schmelzmuster with inner radial enamel like other beavers. Porcupines have thick HSB throughout the enamel layer. This character in the cheek teeth facilitates the separation of isolated beaver teeth from porcupine teeth.

A new record of the enigmatic Eurasian Miocene ruminant artiodactyl Orygotherium

Abstract Hambach 6C, a recently discovered middle Miocene vertebrate locality in northwestern Germany, produced the fourth occurrence of the extremely rare ruminant Orygotherium escheri. The new record is an isolated M3. In Central Europe, O. escheri is known only from lignitic deposits of zone MN5, and may have been restricted to swampy habitats. Figures and measurements of the lecto- and paralectotypes are published for the first time. The phylogenetic position of Orygotherium within the Ruminantia remains uncertain despite 160 years of research.

The castorid Steneofiber from NW Germany and its implications for the taxonomy of Miocene beavers

Craniodental remains of a medium-sized beaver from the early middle Miocene of Hambach (MN 5) in the Lower Rhine Basin of northwestern Germany are described and assigned to Steneofiber depereti. The relatively rich material (6 mandibles and 56 isolated teeth) was collected from a single locality, Hambach 6C, and comprises specimens representing juvenile to very old individuals. This makes it possible to assess the morphologic and metric variability of a single population of Steneofiber depereti. Metrically, the mandibular tooth rows compare favorably in size to those of three subspecies described from the Loire Basin in France: Steneofiber depereti janvieri, Steneofiber d. caliodorensis, and Steneofiber d. depereti. Therefore in our opinion, division into subspecies cannot be applied to S. depereti in general. The difference in size between the smaller beaver from Hambach and the contemporaneous larger S. d. carnutense from the Loire Basin is remarkable. The taxonomy of early middle Miocene medium-sized castorids, referred to Steneofiber depereti, Steneofiber subpyrenaicus, and Chalicomys jaegeri is discussed. The presence of the derived beaver C. jaegeri in MN 4 to MN 6 is questioned and assignment to Steneofiber suggested. The occasional appearance of single C. jaegeri features in S. depereti supports the existence of a European lineage from the Orleanian S. depereti to the Vallesian C. jaegeri. The taxonomic status of S. subpyrenaicus remains unresolved.

Carettochelyine Turtle from the Neogene of Europe

Abstract We identify a fragmentary turtle specimen from the middle Miocene (MN 5) of Hambach, Germany, as the bridge peripheral of a carettochelyine turtle. This important find extends the fossil record of the group to the Neogene of Europe and calls into question the utility of fossil carettochelyids in identifying tropical climate zones.

Potamotherium valletoni (Carnivora, Mammalia) aus dem Oberoligozän von Enspel im Westerwald

KurzfassungDas Teilskelett eines juvenilenPotamotherium valletoni aus den oberoligozänen Seeablagerungen von Enspel im Westerwald wird eingehend beschrieben. Es handelt sich um den bisher stratigraphisch ältesten Nachweis dieses otterartigen Carnivoren. Die taphonomische Analyse des z. T. disartikulierten Teilskelettes läßt darauf schließen, daß die Tierleiche an Land zunächst einer starken Austrocknung ausgesetzt war. Die Zerlegung des Kadavers erfolgte wahrscheinlich durch Raubtiere, und nur Kopf und vordere Rumpfpartie wurden in den See eingeschwemmt und dort eingebettet. Mit dieser taphonomischen Vorgeschichte unterscheidet sich der Fund von den meisten anderen Säugetierskeletten aus Seeablagerungen.AbstractA partial skeleton of a juvenilePotamotherium valletoni is described in detail. It originates from the upper Oligocene (MP 28) lake deposits of Enspel (Westerwald, Germany). The specimen represents the earliest record of this otter like carnivore. The taphonomic analysis of the partial, somewhat disarticulated skeleton suggests that the carcass initially experienced strong desiccation on land. The carcass apparently was divided up by other carnivores before transport into the lake. Thus this specimen differs very much in its mode of preservation from most mammalian skeletons found in lake sediments.

The beaver Anchitheriomys from the Miocene of Central Europe

Abstract New finds of teeth and mandibles of Anchitheriomys from the Hambach opencast lignite mine in Northwest Germany and the first detailed descriptions of other mandibles from South Germany and Switzerland allow a review of the Central European specimens of this rare beaver genus. The metric variation of cheek teeth and especially the great differences in dimensions of incisors can be much better assessed. The observed range in size can be attributed to ontogenetic changes, and all material is assigned to Anchitheriomys suevicus. Stratigraphically, this species is restricted to the early middle Miocene, European Mammalian Neogene biozones MN 5–6.

Ultimate Eocene (Priabonian) chondrichthyans (Holocephali, Elasmobranchii) of Antarctica

ABSTRACT The Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula, is known for its remarkable wealth of fossil remains of chondrichthyans and teleosts. Chondrichthyans seemingly were dominant elements in the Antarctic Paleogene fish fauna, but decreased in abundance from middle to late Eocene, during which time remains of bony fishes increase. This decline of chondrichthyans at the end of the Eocene generally is related to sudden cooling of seawater, reduction in shelf area, and increasing shelf depth due to the onset of the Antarctic thermal isolation. The last chondrichthyan records known so far include a chimeroid tooth plate from TELM 6 (Lutetian) and a single pristiophorid rostral spine from TELM 7 (Priabonian). Here, we present new chondrichthyan records of Squalus, Squatina, Pristiophorus, Striatolamia, Palaeohypotodus, Carcharocles, and Ischyodus from the upper parts of TELM 7 (Priabonian), including the first record of Carcharocles sokolovi from Antarctica. This assemblage suggests that chondrichthyans persisted much longer in Antarctic waters despite rather cool sea surface temperatures of approximately 5°C. The final disappearance of chondrichthyans at the Eocene—Oligocene boundary concurs with abrupt ice sheet formation in Antarctica. Diversity patterns of chondrichthyans throughout the La Meseta Formation appear to be related to climatic conditions rather than plate tectonics.