Wighart von Koenigswald

Cosmopolitanism among Gondwanan Late Cretaceous mammals

Consistent with geophysical evidence for the breaking up of Pangaea, it has been hypothesized that Cretaceous vertebrates on progressively isolated landmasses exhibit generally increasing levels of provincialism, with distinctly heightened endemism occurring at the beginning of the Late Cretaceous. The Cretaceous fossil record from the southern supercontinent of Gondwana has been much too poor to test this hypothesis with regards to mammals (Fig. 1 ). Early Cretaceous mammals are known only from isolated sites in Argentina, Australia,, Cameroon, and Morocco. Apart from several occurrences in South America, knowledge of Late Cretaceous Gondwanan mammals is limited to a single site in India that previously yielded a few specimens of placental mammals,, and a site in Madagascar that previously yielded only one indeterminate tooth fragment. Here we report the occurrence of a highly specialized and distinctive group of extinct mammals, the Sudamericidae (Gondwanatheria), in the Late Cretaceous of Madagascar and India. These new records comprise the first evidence of gondwanatheres outside South America and the first indication of cosmopolitanism among Late Cretaceous Gondwanan mammals. Antarctica may have served as an important Cretaceous biogeographic link between South America and Indo-Madagascar.

Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology

Background The best European locality for complete Eocene mammal skeletons is Grube Messel, near Darmstadt, Germany. Although the site was surrounded by a para-tropical rain forest in the Eocene, primates are remarkably rare there, and only eight fragmentary specimens were known until now. Messel has now yielded a full primate skeleton. The specimen has an unusual history: it was privately collected and sold in two parts, with only the lesser part previously known. The second part, which has just come to light, shows the skeleton to be the most complete primate known in the fossil record. Methodology/Principal Findings We describe the morphology and investigate the paleobiology of the skeleton. The specimen is described as Darwinius masillae n.gen. n.sp. belonging to the Cercamoniinae. Because the skeleton is lightly crushed and bones cannot be handled individually, imaging studies are of particular importance. Skull radiography shows a host of teeth developing within the juvenile face. Investigation of growth and proportion suggest that the individual was a weaned and independent-feeding female that died in her first year of life, and might have attained a body weight of 650–900 g had she lived to adulthood. She was an agile, nail-bearing, generalized arboreal quadruped living above the floor of the Messel rain forest. Conclusions/Significance Darwinius masillae represents the most complete fossil primate ever found, including both skeleton, soft body outline and contents of the digestive tract. Study of all these features allows a fairly complete reconstruction of life history, locomotion, and diet. Any future study of Eocene-Oligocene primates should benefit from information preserved in the Darwinius holotype. Of particular importance to phylogenetic studies, the absence of a toilet claw and a toothcomb demonstrates that Darwinius masillae is not simply a fossil lemur, but part of a larger group of primates, Adapoidea, representative of the early haplorhine diversification.

New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and Sexual Dimorphism

Background Protocetidae are middle Eocene (49–37 Ma) archaeocete predators ancestral to later whales. They are found in marine sedimentary rocks, but retain four legs and were not yet fully aquatic. Protocetids have been interpreted as amphibious, feeding in the sea but returning to land to rest. Methodology/Principal Findings Two adult skeletons of a new 2.6 meter long protocetid, Maiacetus inuus, are described from the early middle Eocene Habib Rahi Formation of Pakistan. M. inuus differs from contemporary archaic whales in having a fused mandibular symphysis, distinctive astragalus bones in the ankle, and a less hind-limb dominated postcranial skeleton. One adult skeleton is female and bears the skull and partial skeleton of a single large near-term fetus. The fetal skeleton is positioned for head-first delivery, which typifies land mammals but not extant whales, evidence that birth took place on land. The fetal skeleton has permanent first molars well mineralized, which indicates precocial development at birth. Precocial development, with attendant size and mobility, were as critical for survival of a neonate at the land-sea interface in the Eocene as they are today. The second adult skeleton is the most complete known for a protocetid. The vertebral column, preserved in articulation, has 7 cervicals, 13 thoracics, 6 lumbars, 4 sacrals, and 21 caudals. All four limbs are preserved with hands and feet. This adult is 12% larger in linear dimensions than the female skeleton, on average, has canine teeth that are 20% larger, and is interpreted as male. Moderate sexual dimorphism indicates limited male-male competition during breeding, which in turn suggests little aggregation of food or shelter in the environment inhabited by protocetids. Conclusions/Significance Discovery of a near-term fetus positioned for head-first delivery provides important evidence that early protocetid whales gave birth on land. This is consistent with skeletal morphology enabling Maiacetus to support its weight on land and corroborates previous ideas that protocetids were amphibious. Specimens this complete are virtual ‘Rosetta stones’ providing insight into functional capabilities and life history of extinct animals that cannot be gained any other way.

Jaw movement in fossil mammals: analysis, description and visualization

A terminology for and visualizations of different mammalian mastication paths are provided, resulting from orientation of attritional and abrasional facets and striation on fossil (and extant) teeth. The occlusal motion of the left lower jaw is considered, and a moderate wear stage (IDAS 3) is used as standard. In contrast to conventional terminologies, the proposed nomenclature differentiates between the inclination and the direction of the lower jaw movement as projected onto a horizontal plane for each phase of the power stroke. The proposed mastication compass attempts to combine three aspects of the power stroke: (1) the number of phases, (2) the occlusal direction, and (3) the inclination of each phase. Descriptions and visualizations are given for several taxa in order to demonstrate its general applicability. The proposed new terminology and the mastication compass simplify comparisons of different modes of mastication in different mammalian taxa.KurzfassungFür den Mastikationsweg fossiler (und rezenter) Bezahnungen der Mammalia wurde eine neue Terminologie und bildliche Darstellung entwickelt, die sich auf die Ausrichtung von Attritions- und Abrasionsfacetten sowie der Striationen auf der Zahnoberfläche stützt. Dabei wird die Bewegung des unteren linken Unterkieferastes in einem mittleren Abkaustadium (IDAS 3) standardmäßig dargestellt. Im Gegensatz zu den bisherigen Beschreibungen, unterscheidet das vorliegende System für jede Phase des Kauzyklus zwischen Richtung und Steigungswinkel in Bezug auf die Sagittalebene bzw. die horizontale Bezugsebene. Der vorgeschlagene Mastkations-Kompass vereinigt dabei die drei hauptsächlichen Aspekte des “power stroke” während der Mastikationsbewegung: (1) die Anzahl der Kauphasen, (2) die Richtung und (3) den Inklinationswinkel jeder einzelnen Phase. Zur Demonstration der vielseitigen Anwendbarkeit des Mastikations-Kompasses, wird dieser beispielhaft für verschiedenste Taxa dargestellt. Er ermöglicht den Vergleich der Mastikationsbewegungen innerhalb unterschiedlicher Säugetiergruppen.

Pedal distal phalanges of the Eocene adapoids Europolemur and Darwinius compared to phalanges of Notharctus and other primates

Pedal distal phalanges of the Eocene adapoids Europolemur and Darwinius from Messel and Notharctus from Wyoming have been compared morphologically and metrically to representatives of all six superfamilies of extant primates. A detailed system of morphological types is established that differentiates pedal distal phalanges. Four major groups and 12 types can be recognised in primates. Primates additionally show a primary interruption of homogeneity (PIH) between the hallux and other pedal rays, as well as two distinct secondary interruptions of homogeneity (SIH) within more lateral pedal rays. Using morphology, PIH and SIH, we have developed a formula for pedal distal phalanges. Differences among Adapoidea are unexpectedly large. Notharctus shows less differentiation in the pedal phalanges than does Europolemur. Our analyses show that both species of Europolemur had a differentiated grooming claw. Preservation of the second distal phalanx in Darwinius is not sufficient for a detailed classification. Despite similarities of the grooming claws of Europolemur to those of some lemurs and lorises, we hesitate to classify adapoids with Lemuroidea and Lorisoidea as there are significant differences and a possibility of parallelism.

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 microstructure of enamel, dentine and cementum in advanced Taeniodonta (Mammalia) with comments on their dietary adaptations

ABSTRACT n The cheek teeth of Ectoganus and Stylinodon, the most derived genera of Taeniodonta following recent phylogenies, show various morphological and microstructural characteristics that are unusual for herbivores of their size. Their continuously growing premolars and molars have blunt occlusal surfaces without shearing facets and enamel is restricted to the lingual and buccal sides of the teeth. The anterior and posterior walls of the teeth are covered with a thick layer of cementum to which the periodontal ligament is attached. The enamel band is relatively thin. The schmelzmuster is one-layered and features weakly developed Hunter-Schreger bands that are only recognizable in longitudinal section. In cross-section, the enamel prisms show a ‘keyhole pattern’ with an incomplete prism sheath. There is no interprismatic matrix. The microstructure of the dentine has the regular mammalian pattern and shows no special similarity to that of xenarthrans. Taeniodonts seem to have used their hypsodont cheek teeth almost exclusively for squeezing and some crushing of food and only to a minor degree for grinding. Weakly developed Hunter-Schreger bands indicate only light loading during mastication.

Tooth Enamel Microstructure of Living and Extinct Hyracoids Reveals Unique Enamel Types Among Mammals

Among medium- to large-sized terrestrial ‘ungulates,’ there is often a relationship between increasing body size, correlated changes in diet, and increased complexity of the enamel microstructures [notably the development of Hunter-Schreger bands (HSB)]. An exhaustive survey of the enamel microstructures of living and extinct Hyracoidea demonstrates, however, that the Schmelzmuster within this order of mammals is generally one-layered and formed by radial enamel despite a large range of body sizes and dietary adaptations; HSB are remarkably absent. Radial enamel is characteristic of early diverging hyracoids, as well as more derived members of the extinct families Geniohyidae and Pliohyracidae, and the extant Procaviidae. Only some large ‘Saghatheriidae,’ and all members of the family Titanohyracidae, developed a more complex enamel microstructure (i.e., with prisms decussating), a unique condition among Mammalia that we name ‘bundled enamel’ (BE). This structure is reminiscent to some degree of both the ‘Pyrotherium enamel’ and the ‘3D enamel’ of proboscideans. Hyracoids with BE represented a major component of the diversity of mid- to large-sized herbivores during the Paleogene in Africa. Like HSB, which are developed by most other ‘ungulates,’ the BE is regarded as a device for resisting propagation of cracks during mastication. Hyracoids never developed however the ‘modified radial enamel’ that is characteristic of most large and hypsodont perissodactyls and artiodactyls that entered Africa during the Miocene.

Dental Function and Diet of Vintana Sertichi (Mammalia, Gondwanatheria) from the Late Cretaceous of Madagascar

ABSTRACT—The nearly complete and well-preserved cranium of Vintana sertichi provides an opportunity to investigate its dietary adaptations. We used a combination of comparative morphological and biomechanical analyses to reveal the direction of its power stroke during mastication, reconstruct the positions and relative sizes of its muscles of mastication, and predict its capacity to produce bite forces during incision and molariform occlusion. The orientation of dental wear striations on the upper molariform teeth of Vintana, in combination with the orientation of the enamel islets and synclines and the position of leading and trailing edges, demonstrates that the power stroke was primarily palinal (distally directed), with a significant buccally directed component that is absent in multituberculates, haramiyidans, and other gondwanatherians. The large palinal component of jaw movement was corroborated by biomechanical analyses of the moments generated by the primary jaw adductors around the dentary-squamosal joint axis. Similar analyses also confirmed the previously documented proal (mesially directed) power stroke of the extant rodent Myocastor. Finite element analyses predict that Vintana was capable of producing bite forces that were more than twice as high as the similarly sized Myocastor. Vintana was almost certainly an herbivore, as claimed previously for other sudamericid gondwanatherians. Its size and capacity to generate high bite forces at both the incisors and the molariform teeth suggest that it was a mixed feeder whose diet may have included relatively large, hard food items such as roots, seeds, twigs, or nut-like fruits.

Enamel Microstructure of Vintana Sertichi (Mammalia, Gondwanatheria) From the Late Cretaceous of Madagascar

ABSTRACT The enamel microstructure of the molariform cheek teeth of Vintana sertichi (Gondwanatheria, Mammalia) from the Late Cretaceous of Madagascar retains many of the plesiomorphic characteristics of mammalian prismatic enamel (e.g., single-layered schmelzmuster; non-decussating, small prisms). However, V. sertichi exhibits a relatively derived condition and resembles Lavanify miolaka (Late Cretaceous, Madagascar), Bharattherium bonapartei (Late Cretaceous, India), and an indeterminate sudamericid (Late Cretaceous, Madagascar) in possessing modified radial enamel, consisting of prisms separated by prominent interrow sheets of interprismatic matrix. A second group of gondwanatherians (Ferugliotherium windhauseni, Gondwanatherium patagonicum, Sudamerica ameghinoi, Greniodon sylvaticus), all from the Late Cretaceous and Paleogene of Argentina, retains relatively primitive, ‘normal’ radial enamel, in which the interprismatic matrix anastomoses around the prisms and does not form interrow sheets. The prisms of gondwanatherian molariforms generally become wider from the enamel-dentine junction to the outer enamel surface, dramatically so in Gondwanatherium. Seams are very rare; tubules are more common. Prism decussation has not been found in any gondwanatherian enamel. Gondwanatherian molariforms lack or have only a thin layer of external prismless enamel, although it is thick in the incisors of Sudamerica. Despite their apparent utility in differentiating among gondwanatherian taxa, or gondwanatherians as a whole from other clades, many of the derived characteristics of gondwanatherian enamel microstructure are found in other mammalian groups and may reflect a high degree of homoplasy.