Kretzoiarctos gen. nov., the Oldest Member of the Giant Panda Clade

The phylogenetic position of the giant panda, Ailuropoda melanoleuca (Carnivora: Ursidae: Ailuropodinae), has been one of the most hotly debated topics by mammalian biologists and paleontologists during the last century. Based on molecular data, it is currently recognized as a true ursid, sister-taxon of the remaining extant bears, from which it would have diverged by the Early Miocene. However, from a paleobiogeographic and chronological perspective, the origin of the giant panda lineage has remained elusive due to the scarcity of the available Miocene fossil record. Until recently, the genus Ailurarctos from the Late Miocene of China (ca. 8–7 mya) was recognized as the oldest undoubted member of the Ailuropodinae, suggesting that the panda lineage might have originated from an Ursavus ancestor. The role of the purported ailuropodine Agriarctos, from the Miocene of Europe, in the origins of this clade has been generally dismissed due to the paucity of the available material. Here, we describe a new ailuropodine genus, Kretzoiarctos gen. nov., based on remains from two Middle Miocene (ca. 12–11 Ma) Spanish localities. A cladistic analysis of fossil and extant members of the Ursoidea confirms the inclusion of the new genus into the Ailuropodinae. Moreover, Kretzoiarctos precedes in time the previously-known, Late Miocene members of the giant panda clade from Eurasia (Agriarctos and Ailurarctos). The former can be therefore considered the oldest recorded member of the giant panda lineage, which has significant implications for understanding the origins of this clade from a paleobiogeographic viewpoint

Modeling the Adaptive Role of Negative Signaling in Honey Bee Intraspecific Competition

Collective decision making in the social insects often proceeds via feedback cycles based on positive signaling. Negative signals have, however, been found in a few contexts in which costs exist for paying attention to no longer useful information. Here we incorporate new research on the specificity and context of the negative stop signal into an agent based model of honey bee foraging to explore the adaptive basis of negative signaling in the dance language. Our work suggests that the stop signal, by acting as a counterbalance to the waggle dance, allows colonies to rapidly shut down attacks on other colonies. This could be a key adaptation, as the costs of attacking a colony strong enough to defend itself are significant

Les Rhinocerotidae (Mammalia, Perissodactyla) miocènes et pliocènes des Tugen Hills (Kénya)

More than 70 determinable and usable rhinoceros remains belonging to nine species were yielded by 26 Miocene and Pliocene sites from the Tugen Hills (Kenya), namely Cheboit, Kapsomin, Kipsaraman and Tabarin. Such a material allows a better knowledge of the anatomy of these species. It is now possible to distinguish the postcranial skeleton of <i>Aceratherium acutirostratum</i> from that of <i>Dicerorhinus leakeyi</i>. The cranial and dental anatomy of <i>Paradiceros mukirii</i> is better known. The temporal extension of <i>Chilotheridium pattersoni</i> and <i>Paradiceros mukirii</i> are increased. <i>Ceratotherium praecox</i> is the most frequent rhino from the Uppermost Miocene onwards. <i>Diceros bicornis</i> is known since 6 My, about at the same time the first <i>C. praecox. Diceros</i> cf. <i>pachygnathus</i> is identified in the Lukeino and Mabaget Formations, and the geographical extension of this group of species is much increased. The Hominid Orrorin tugenensis is associated with rhinoceroses in four sites of the Lukeino Formation; <i>Ceratotherium praecox</i> is present in three of them, alone in Kapcheberek, associated one time (Tabarin) with <i>D. bicornis</i> and in another one (Cheboit) with <i>Brachypotherium lewisi</i>; at Aragai the sole rhino is <i>Diceros</i> cf. <i>pachygnathus</i>. All these rhinos contribute to assign to <i>Orrorin</i> a variable but mostly open and rather wet palaeoenvironment.<br><br>[fr] Plus de 70 restes déterminables appartenant à neuf espèces de Rhinocerotidae ont été recueillis dans 26 gisements miocènes et pliocènes des Tugen Hills, les plus riches étant Cheboit, Kapsomin, Kipsaraman et Tabarin. Ce matériel permet d’accroître sensiblement nos connaissances sur l’anatomie de ces espèces. Il est désormais possible de distinguer le squelette post-crânien de <i>Aceratherium acutirostratum</i> de celui de <i>Dicerorhinus leakeyi</i>; l’anatomie crânienne et dentaire de <i>Paradiceros mukirii</i> est mieux connue. L’extension temporelle de <i>Chilotheridium pattersoni</i> et de <i>Paradiceros mukirii</i> sont sensiblement accrues. <i>Ceratotherium praecox</i> est le rhinocéros le plus fréquent à partir du Miocène terminal. <i>Diceros bicornis</i> est attesté depuis 6 Ma, sensiblement au même moment que les premiers <i>C. praecox</i>. <i>Diceros</i> cf. <i>pachygnathus</i> est reconnu dans les formations de Lukeino et de Mabaget, ce qui accroît considérablement l’extension géographique des espèces de ce groupe. L’association de l’Hominidé Orrorin tugenensis avec Ceratotherium praecox dans trois des quatre sites où il a été découvert (et, dans un seul site à chaque fois, avec <i>Diceros</i> cf. <i>pachygnathus, D. bicornis</i> et <i>Brachypotherium lewisi</i>) montre que son environnement végétal était varié mais à dominante ouverte et plutôt humide

Old world ruminant morphophysiology, life history, and fossil record: exploring key innovations of a diversification sequence

The omasum of pecoran ruminants (which is absent in tragulids) and shorter gestation periods in non-giraffid crown pecorans (as opposed to giraffids) could represent cases of key innovations that caused disparity in species diversity in extant ruminants. Literature suggests that the different ruminant groups inhabited similar niche spectra at different times, supporting the ‘increased fitness’ interpretation where a key innovation does not mainly open new niches, but allows more efficient use of existing ones. In this respect, we explored data on fossil species diversity of Afro-Eurasian ruminants from the Neogene and Quaternary. Tragulid and giraffid diversity first increased during the Early/Middle Miocene with subsequent declines, whereas bovid and cervid diversity increased distinctively. Our resulting narrative, combining digestive physiology, life history and the fossil record, thus provides an explanation for the sequence of diversity patterns in Old-World ruminants