TURTLES: LIVING FOSSILS

Turtle ribs fuse together with some of their vertebrae so they have to pump air in and out of the lungs with their leg muscles instead?

Another unusual feature in turtles is their limb girdles (pectoral and pelvic) have come to lie 'within' their rib cage, a feature that allows some turtles to pull its limbs inside the shell for protection. Sea turtles didn't develop this behaviour (or ability) and do not retract into their shells like other turtles.

Turtle shells are different from the armoured “shells” we see on dinosaurs like the ankylosaurs. Turtles are covered by a special bony or cartilaginous shell developed from their ribs that acts as a shield. It is fundamentally different from the armour seen on our other vertebrate pals. Turtle armour is made of dermal bone and endochondral bones of the vertebrae and rib cage.

Armadillos have armour formed by plates of dermal bone covered in relatively small, overlapping epidermal scales called "scutes," composed of bone with a covering of horn. In crocodiles, their exoskeletons form their armour. It is made of protective dermal and epidermal components that begin as rete Malpighii: a single layer of short, cylindrical cells that lose their nuclei over time as they transform into a horny layer.

Depending on the species and age of the turtle, turtles eat all kinds of food including seagrass, seaweed, crabs, jellyfish, and shrimp,. That tasty diet shows up in the composition of their armour as they have oodles of great nutrients to work with. The lovely example you see here is from the Oxford Museum collections.

CRETACEOUS HADROSAUR TOOTH

A rare and very beautifully preserved Cretaceous Hadrosaur Tooth. This lovely specimen is from one of our beloved herbivorous "Duck-Billed" dinosaurs from 68 million-year-old outcrops near Drumheller, Alberta, Canada — and is likely from an Edmontosaurus.

When you scour the badlands of southern Alberta, most of the dinosaur material you'll find are from hadrosaurs. These lovely tree-less valleys make for excellent-searching grounds and have led us to know more about hadrosaur anatomy, evolution, and paleobiology than for most other dinosaurs. 

We have oodles of very tasty specimens and data to work with. We've got great skin impressions and scale patterns from at least ten species and interesting pathological specimens that provide valuable insights into hadrosaur behaviour. These herbivorous beauties are also found in Europe, South America, Mexico, Mongolia, China and Russian. Together, this abundance of specimens has provided great insight into their evolution, dining habits and social preferences. We know they liked to live in herds. They were terrestrial but also water babies — paddling around in freshwater pools to snack on the tasty greenery that lined its sides. They had adapted webbing in their feet to be as nimble on land as they were in the water. 

There are papers on all aspects of hadrosaurian life and not surprisingly — given the ideal collecting grounds — many of those papers focus on our Canadian finds. Hadrosaurs had teeth arranged in stacks designed for grinding and crushing, similar to how you might picture a cow munching away on the grass in a field. These complex rows of "dental batteries" contained up to 300 individual teeth in each jaw ramus. But even with this great number, we rarely see them as individual specimens.

They didn't appear to shed them all that often. Older teeth that are normally shed in our general understanding of vertebrate dentition, were resorped, meaning that their wee osteoclasts broke down the tooth tissue and reabsorbed the yummy minerals and calcium.

As the deeply awesome Mike Boyd notes, "this is an especially lucky find as hadrosaurs did not normally shed so much as a tooth, except as the result of an accident when feeding or after death. Typically, these fascinating dinosaurs ground away their teeth... almost to nothing."

In hadrosaurs, the root of the tooth formed part of the grinding surface as opposed to a crown covering over the core of the tooth. And curiously, they developed this dental arrangement from their embryonic state, through to hatchling then full adult.

There's some great research being done by Aaron LeBlanc, Robert R. Reisz, David C. Evans and Alida M. Bailleul. They published in BMC Evolutionary Biology on work that looks at the histology of hadrosaurid teeth analyzing them through cross-sections. Jon Tennant did a nice summary of their research. I've included both a link to the original journal article and Jon Tennant's blog below.

LeBlanc et al. are one of the first teams to look at the development of the tissues making up hadrosaur teeth, analyzing the tissue and growth series (like rings of a tree) to see just how these complex tooth batteries formed.

They undertook the first comprehensive, tissue-level study of dental ontogeny in hadrosaurids using several intact maxillary and dentary batteries and compared them to sections of other archosaurs and mammals. They used these comparisons to pinpoint shifts in the ancestral reptilian pattern of tooth ontogeny that allowed hadrosaurids to form complex dental batteries.

References:

LeBlanc et al. (2016) Ontogeny reveals function and evolution of the hadrosaurid dinosaur dental battery, BMC Evolutionary Biology. 16:152, DOI 10.1186/s12862-016-0721-1 (OA link)

To read more from Jon Tennant, visit: https://blogs.plos.org/paleocomm/2016/09/14/all-the-better-to-chew-you-with-my-dear/

Photo credit: Derrick Kersey. For more awesome fossil photos like this from Derrick, visit his page: https://www.facebook.com/prehistoricexpedition/

ZENAPSIS MORTALITY PLATE

A Devonian fish mortality plate showing all lower shields of Zenaspis podolica (Lankester, 1869) and Stensiopelta pustulata (or Victoraspis longicornualis) from Lower Devonian deposits of Podolia, Ukraine.

Zenaspis is an extinct genus of jawless fish which existed during the early Devonian period. Due to it being jawless, Zenaspis was probably a bottom feeder.

The lovely 420 million-year-old plate you see here is from Podolia or Podilia, a historic region in Eastern Europe, located in the west-central and south-western parts of Ukraine, in northeastern Moldova. Podolia is the only region in Ukraine where Lower Devonian remains of ichthyofauna can be found near the surface.

For the past 150 years, vertebrate fossils have been found in more than 90 localities situated in outcrops along banks of the Dniester River and its northern tributaries, and in sandstone quarries. At present faunal list of Early Devonian agnathans and fishes from Podolia number 72 species, including 8 Thelodonti, 39 Heterostraci, 19 Osteostraci, 4 Placodermi, 1 Acanthodii, and 1 Holocephali (Voichyshyn 2001a, modified).

In Podolia, Lower Devonian redbeds strata (the Old Red Formation or Dniester Series) can be found up to 1800 m thick and range from Lochkovian to Eifelian in age (Narbutas 1984; Drygant 2000, 2003). In the lower part (Ustechko and Khmeleva members of the Dniester Series) they consist of multicoloured, mainly red, fine-grained cross-bedded massive quartz sandstones and siltstones with seams of argillites (Drygant 2000).

We see fossils beds of Zenaspis in the early Devonian of Western Europe. Both Zenaspis pagei and Zenaspis poweri can be found up to 25 centimetres long in Devonian outcrops of Scotland.

Reference: Voichyshyn, V. 2006. New osteostracans from the Lower Devonian terrigenous deposits of Podolia, Ukraine. Acta Palaeontologica Polonica 51 (1): 131–142. Photo care of Fossilero Fisherman.

HADROSAURUS OF THE UPPER CRETACEOUS NANAIMO GROUP

Hadrosaurus, also known as the "duck-billed" dinosaurs, were a very successful group of plant-eaters that thrived throughout western Canada during the late Cretaceous, some 70 to 84 million years ago. Hadrosaurs may have lived as part of a herd, dining on pine needles, twigs and flowering plants.

There are two main groups of Hadrosaurs, crested and non-crested. The bony crest on the top of the head of the hadrosaurs was hollow and attached to the nasal passages. It is thought that the hollow crest was used to make different sounds. These sounds may have signalled distress or been the mating calls used to attract mates. Given their size it would have made for quite the trumpeting sound.

This beautiful specimen graces the back galleries of the Courtenay and District Museum on Vancouver Island, British Columbia, Canada. I was very fortunate to have a tour this past summer with the deeply awesome Mike Trask joined by the lovely Lori Vesper. The museum houses an extensive collection of palaeontological and archaeological material found on Vancouver Island, many of which have been donated by the Vancouver Island Palaeontological Society.

Dan Bowen, Chair of the Vancouver Island Palaeontological Society, shared a photo of the first partly articulated dinosaur from Vancouver Island ever found. The research efforts of the VIPS run deep in British Columbia and this new very significant find is no exception. A Hadrosauroid dinosaur is a rare occurrence and further evidence of the terrestrial influence in the Upper Cretaceous, Nanaimo Group, Vancouver Island.

This fossil bone material was found years ago by Mike Trask of the Vancouver Island Palaeontological Society. You may recall that he was the same fellow who found the Courtenay elasmosaur. The bone was initially thought to be a plesiosaur but turned out to be a hadrosauroid. The find was confirmed by hadrosaur authority Dr. David Evans, senior curator of the Royal Ontario Museum.
You can see the articulated Hadrodauriod fossil bone Mike found now prepped fully prepped.

This fellow has kissing cousins over in the state of New Jersey where this species is the official state fossil. The first of his kind was found by John Estaugh Hopkins in New Jersey back in 1838.