Scientific Illustration

Der Schädel von Glyptodon. Meyer, H. von. 1865. Palaeontographica 14(2):1-18

Newly Described Eunotosaurus africanus Material

The turtle has been in no rush to give up the secret of its shell — but after two centuries of close study, scientists are filling in the story of a structure unique in the history of life.

New research led by Tyler Lyson of Yale University and the Smithsonian Institution pushes back the origins of the turtle shell by about 40 million years, linking it to Eunotosaurus, a 260-million-year-old fossil reptile from South Africa. The work strengthens the fossil record and bolsters an existing theory about shell development while providing new details about its precise evolutionary pathway.

“Now we’ve got an intermediate shell, a transitional form that bridges the gap between turtles and other reptiles and helps explain how the turtle shell evolved,” said Lyson, a curatorial affiliate of the Yale Peabody Museum of Natural History and a Smithsonian postdoctoral researcher. “Eunotosaurus is an early offshoot of the lineage that gave rise to modern turtles — it’s an early stem turtle.”

http://news.yale.edu/2013/05/30/how-turtle-got-its-shell

Evolutionary Origin of the Turtle Shell. Lyson, Tyler R.; Bever, Gabe S.; Scheyer, Torsten M.; Hsiang, Allison Y.; Gauthier, Jacques A. Current biology : CB doi:10.1016/j.cub.2013.05.003 

Evolutionary Developmental Model for the Origin of the Turtle Shell

“Results of a phylogenetic analysis of shelled reptiles and characters important in constructing a shell are plotted against the ontogeny of pleurodire turtles. Thin sections through turtle embryos show the initial outgrowth of (sub)dermal bone through the costals first (carapace length [CL] = 13.0mm in the pleurodire Emydura subglobosa) and then the neurals (CL = 18.0 mm in the pleurodire Pelomedusa subrufa). The timing of ontogenetic transformations of those features (in red) important in the construction of the shell (i.e., the number of dorsal vertebrae or ribs does not change through ontogeny) is congruent with the phylogenetic transformation of those same features based on our recovered tree topology. Our model makes explicit morphological and histological predictions for the lineage prior to the most recent common ancestor of Eunotosaurus africanus and turtles that are met by the morphology found in Milleretta rubidgei. Numbers above each node represent bootstrap frequencies obtained in the phylogenetic analysis.”

Evolutionary Origin of the Turtle Shell Lyson, Tyler R.; Bever, Gabe S.; Scheyer, Torsten M.; Hsiang, Allison Y.; Gauthier, Jacques A. Current biology : CB doi:10.1016/j.cub.2013.05.003 

See also:

How the turtle got its unique hard shell

http://news.yale.edu/2013/05/30/how-turtle-got-its-shell

mucholderthen:

THE PENCIL SHARPENER ANOMALOCARID
505 mya - mid-Cambrian |  everywhere

Hurdia victoria
by =avancna

Hurdia was one of the largest organisms in the Cambrian oceans, reaching approximately 50 cm (1.5 feet) in length. Its head bore a pair of spiny claws which shoveled food into its pineapple-ring-like mouth.

A hollow, spike-shaped shell protruded from the front of its head.

Die Kreidefauna des Peterwardeiner Gebirges

Palaeontographica 52 (1905-6)

biologicalmarginalia:

This Early Miocene sunfish, Austromola angerhoferi, is estimated to have a total length of 3.2 meters (10’6”), making it the largest known Cenozoic teleost fossil. Mola mola can get somewhat larger — 3.33 m — although considering Austromola is know from only three specimens (the others being 1.5–1.7 and 2.4 m), I’d imagine it was considerably larger on average. Austromola is essentially “modern” in shape, although with some minor plesiomorphic traits (more vertebrae, hexagonal scales).

Gregorova, R. et al. (2009) A giant Early Miocene sunfish from the North Alpine Foreland Basin (Austria) and its implication for molid phylogeny. Journal of Vertebrate Paleontology 29(2) 359–371.

mucholderthen:

Palaeopagurus vandelenengeli
Lower Cretaceous hermit crab in an Ammonite shell
by =avancna

Based on In situ fossil hermit crabs (Paguroidea) from northwest Europe and Russia  [PDF]

The Hauterivian (Lower Cretaceous) hermit crab, Palaeopagurus vandelenengeli, in a simberskitine ammonite shell.

From the Speeton Clay Beds of Speeton, Yorkshire England.

marywilliams:

Finished this little guy earlier today. Not my favorite, but he’s okay. I need more practice with patience regarding these sorts of detailed critters. Mostly I think I just don’t like drawing animals with lots of segments… Hmmm…

8.5” x 11” 

Cored pencil and digital.

mucholderthen:

Hispaniola Sloths 01
by =avancna

Various pygmy ground sloths from the island of Hispaniola.

• Acratocnus ye (largest)
• Neocnus dousman (on log)
• N. toupiti (smallest)

Polycystins, figures of remarkable forms &c. in the Barbados chalk deposit (chiefly collected by Dr. Davy, and noticed in a lecture delivered to the Agricultural Society of Barbados, in July, 1846) by BioDivLibrary on Flickr.

London :W. Wheldon,[ca. 1869].
biodiversitylibrary.org/page/9996058