Neurobiological approaches in vertebrate paleontology

The study of the central nervous system in extinct vertebrates is discussed. Historical development of the nervous system is restricted to a few morphological patterns. The foundation of structural conservatism of the nervous system is provided by the multifunctional character of any adaptive changes in the brain of vertebrates. The functional structural features allow the use of the nervous system for the resolution of some difficult questions of vertebrate evolution.     

A new elusive otodontid shark (Lamniformes: Otodontidae) from the lower Miocene,and comments on the taxonomy of otodontid genera,including the ‘megatoothed’ clade

We describe a new large otodontid lamniform shark, Megalolamna paradoxodon gen. nov. et sp. nov., chronostratigraphically restricted to the early Miocene (Aquitanian–Burdigalian). This new species is based on isolated teeth found from five globally distributed localities: the Jewett Sand in southern California, USA; the Pungo River Formation of North Carolina, USA; the Chilcatay Formation of Peru; the Oi Formation in Mie Prefecture, Japan; and the O’oshimojo Formation in Nagano Prefecture, Japan. Extrapolations based on available published data on modern macrophagous lamniforms suggest that the largest specimen of M. paradoxodon gen. nov. et sp. nov. possibly came from an individual that measured at least 3.7 m in total length. All specimens came from deposits in the mid-latitudinal zones representing shallow-water, shelf-type, coastal environments. Its dentition likely exhibited monognathic heterodonty suited for capturing and cutting relatively large prey (e.g. medium-sized fishes). We recommend the genus Otodus to include sharks of the ‘megatoothed’ (e.g. megalodon) lineage in order to avoid Otodus paraphyly. We also propose the following phylogenetic hypothesis: [Kenolamna?+?[Cretalamna?+?[Megalolamna + Otodus]]].

ZooBank LSID for the genus Megalolamna is: urn: lsid:zoobank.org:act:B4791DEF-4D96-4FEB-9B7B-0EF816B96079

ZooBank LSID for the species Megalolamna paradoxodon is: urn:lsid:zoobank.org:act:7D3D7442-53C6-43A2-9E8D-6339729565B6     

The importance of the “Gegenbaur school” for German morphology

Summary The school Carl Gegenbaur cultivated at Heidelberg (1873–1901) was critical to the history of German morphology in multiple ways. During and after his lifetime, the school carried out detailed comparative anatomical and embryological investigations in an evolutionary framework, thereby contributing substantially to the project of vertebrate evolutionary morphology. Its members also defended their mentor when his ideas came under attack. After his death, they labored to perpetuate his program and his memory in the increasingly unwelcoming environment of medical education and research. While the senior members of the school did this largely through institutional means-seeking to place Gegenbaur sympathizers in academic and editorial positions-its junior members absorbed some of the criticisms of the school to develop a modified, more functional approach to evolutionary morphology. The school thus kept the Gegenbaur program alive and active in the German-speaking lands for over fifty years. This paper is drawn largely from Nyhart (1995), esp. chapter 7 (supported by NSF award no. 8910873). Information not otherwise documented derives from this book.     

A reclassification of the anomopod families Macrothricidae and Chydoridae,with the creation of a new suborder,the Radopoda (Crustacea: Branchiopoda)

An investigation, using optical microscopy and SEM, of the trunk limbs of the Anomopoda has revealed a large number of characters, previously underused or unused in taxonomy and comparative morphology. All these characters, which are nicely paralleled by some more conventional traits (head shield and pores, postabdomen, antennae ...), show one clear tendency across all groups studied: a state of complexity at one extreme, and a state of often incisive simplification at the other extreme, with a number of transitional stages in between. The complex character state, which itself is a simplification of the leg structure of the Ctenopoda and other, large Branchiopoda, is here considered to represent a primitive condition. The simplified state is considered advanced. Based on this assumption, we list a number of unifying characters (mainly structural aspects of P1 and P2, but also the gnathobase of P3 and P4) for all macrothricid and chydorid-like anomopods, which we unite in the new suborder Radopoda. Non-radopod Anomopoda are not reclassified. We then derive a cascade of (mainly trunk-limb based) characters to work out a hypothesis on the evolution of the Radopoda. The chydorid line (basically the former family Chydoridae) is classified as a superfamily (the Eurycercoidea), with three families; the macrothricid line is capped by the superfamily Macrothricoidea, with four families. Of these seven families, four are upgraded from subfamily status, the Chydoridae are left status quo, the Macrothricidae are redefined, and the Neothricidae are a new family. The Macrothricidae are further subdivided in two subfamilies, of which the Macrothricinae appear reasonably homogeneous (monophyletic), while the non-Macrothricinae require further study. Some of these (e.g. Guernella) have almost completely lost their P5, a situation parallel to that of the P6 in the Eurycercidae, Acantholeberidae, and Ophryoxidae.