Mixosaurus specially adapted to eat squid

A recent arrival in the library is a wonderful monograph on the family Mixosauridae published late last year in the Swiss Memoirs of Paleontology vol. 124 (Schweizeriche Palaeontologische Abhandlungen) by Winand Brinkmann. The Monograph highlights the nice fossils of this rare marine reptile family from the middle Triassic of the Southern Alps in the Monte San Giorgio area. Mixosauridae have highly derived posterior dentitions composed of large pointed teeth for soft food and small blunt teeth for hard food. They were specially adapted for eating coleoid squids, a hypothesis confirmed by the presence of squid tentacle hooks in the stomach contains of one specimen.

Miocene Fauna gets big press.

I was excited to see the press pick up a story on the discovery of a diverse Miocene fauna from California. See this list of links from Google.

Paleoclimatic Reconstruction Using Fossil Vertebrates

Using multipe regression analysis Manuel Fernandez and Pablo Palaez-Carnpomanes recently published a research paper in Global Ecology and Biogeography which uses fossil mammalian faunas to calculate climatic conditions of the early Pleistocene of Europe. A species by climate matrix is constructed. Each species and climate entry is represented with 0 (species does not live in the climatic zone) or 1/n where n is the number of climates that the species is found in. In this study 13 climatic variables were used. A multivariate analysis is then run on the matrix to correlate species occurence with climate. The authors concluded that rodents and other small mammals provide the most accurate estimation of past climatic conditions.

Mammal Ear Bones, evolved once, twice or three times?

Mammals have three ear bones (stapes, malleus, and incus) that lay in the air filled cavity called the middle ear. Sound is transported through these bones from the tympanic membrane ("ear drum") to the fluid filled inner ear. A remarkible early Cretacoues fossil mammal (reported in the Feb. 11th issue of Science by Tom Rich et al.) from Victoria, Australia, Teinolophos, exhibits a prominent mandidular trough and well-developed ridge that implys that the middle ear bones were still in contact with the lower jaw. This is not all that surprising since Jurassic mammals such as Morganucodon and Docodon have this primitive feature as well. Yet, based on the "funky" morphology of the teeth, Teinolophos is closely related to living Monotremes. If one excepts a cladogram that places Tricondonts (our Dinosaur eating mammal, see previous post), Multituberculates, Symmetrodonts, Dryolestids, Amphiterium, Marsupials and Placentals into a clade (called Theriimorpha) and Teinolophos and modern Monotremes in a sister clade, the detachment of the ear bones from the lower jaw must have occured twice, once in the ancestor of Monotremes, and once in the ancestor of "Theriimorpha." Although even if you used an alternate cladogram, you only get ear bones detaching from the lower jaw once if you place Teinolophos as the ancestor of all the other mammal groups, but then you would have to neglect all the other characters of Teinolophos, such as those "funky" teeth that place it with Monotremes.

In memory of Ernst Mayr.

I saw this great essay http://www.sciencemag.org/cgi/content/full/305/5680/46 by Ernst Mayr, written on his 100th birthday last year. He was the last living scientist from the "golden age of the Evolutionary Synthesis." He concludes his essay with the following statement. "The new research has one most encouraging message for the active evolutionist: it is that evolutionary biology is an endless frontier and there is still plenty to be discovered. I only regret that I won't be present to enjoy these future developments."

Another cladogram, but no new fossils

Jean-Renaud Boisserie and colleages published in the most current issue of the Proceedings of the National Academy of Sciences of the USA a peculiar little article where they present a new cladogram on the "Cetartiodactyla" hypothesis.
Over the last three years there has been a paradigm shift in the theories regarding the origin of whales; that they are true Artiodactyls and most closely related to Hippopotami rather than evolving from archaic ungulates. However, little is known of fossil Hippopotami before the early Miocene. A geological gap occurs in subsahara Africa from the Cretaceous to early Miocene. This gap has left a mystery for early Artiodactyla evolution. Yet rather than state this preservational gap in the fossil record, the authors bemoan other researchers, while presenting their own ideas with a cladogram, without the addition of new fossils. Their study still leaves the mystery... how the tiny early artiodactyl Diacodexis became the whale Pakicetus in such a short amount of time. And is there a Paleocene diversification of artiodactyls that we don't know about in Africa?