The Very Strange Adalatherium hui

This week, has seen the publication in the journal “Nature” of a scientific paper describing a new species of bizarre mammal from the Late Cretaceous of Madagascar.  Named Adalatherium (A. hui), this cat-sized animal shared its island home with a variety of predators such as abelisaurid dinosaurs, crocodilians and snakes.  At an estimated three kilograms, Adalatherium was no giant, but the fossilised remains, which represent a near complete skeleton of an individual, indicate that this mammal was not yet fully mature when it died and as such, it is one of the largest members of the crown group of mammals described from Upper Cretaceous material.

Adalatherium hui

A Life Reconstruction of Adalatherium (A. hui)

Picture credit: Reuters

Madagascar became isolated from the rest of Gondwana around 88 million years ago.  Animals on the island were effectively marooned and many pursued a different evolutionary route compared to related forms on the rest of the super-continent.  Classified as a member of the Gondwanatheria, an extinct group of mammaliaforms confined to the southern hemisphere and up until now, only known from isolated teeth and fragmentary bones, the Adalatherium lineage developed an unusual and unique set of characteristics never seen before in a tetrapod.

“Crazy Beast”

The backbone has more vertebrae than any other Mesozoic mammal and one of its rear leg bones (tibia) was bowed.  How this animal moved around is a bit of a mystery, but the authors of the scientific paper suggest that this animal lived in burrows (fossorial).  The snout shows a mixture of primitive and very advanced anatomical traits.  Adalatherium had more foraminia, small holes in the nasal cavity that served as passageways for nerves and blood vessels, than any other mammal extinct or living today.

The snout was probably extremely sensitive and covered in whiskers, they may have helped it find its way about underground.  One foramen (hole for nerves or blood vessels), at the top of the snout has no know parallel with any other mammal.

These strange characteristics inspired the researchers to name this animal “crazy beast” from the local Malagasy and from the Greek.

The Preserved Skeleton of Adalatherium and Accompanying Line Drawing

Picture credit: Krause et al.

Adalatherium hui – Bending and Breaking a Lot of Rules

Corresponding author, Dr David Krause (Denver Museum of Nature and Science), commented:

“Knowing what we know about the skeletal anatomy of all living and extinct mammals, it is difficult to imagine that a mammal like Adalatherium hui could have evolved, it bends and even breaks a lot of rules.”

Dr Krause is no stranger to bizarre prehistoric animals from Madagascar.  In 2008, Everything Dinosaur wrote a blog post about the “frog from Hell”, a research team led by Dr Krause had discovered the fossilised remains of a giant frog that inhabited the Late Cretaceous of Madagascar.

To read more about this: Beelzebufo ampinga – a frog that could jump continents!

The scientific paper: “Skeleton of a Cretaceous mammal from Madagascar reflects long-term insularity” by David W. Krause, Simone Hoffmann, Yaoming Hu, John R. Wible, Guillermo W. Rougier, E. Christopher Kirk, Joseph R. Groenke, Raymond R. Rogers, James B. Rossie, Julia A. Schultz, Alistair R. Evans, Wighart von Koenigswald and Lydia J. Rahantarisoa published in the journal Nature.

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Ptychodontid Sharks Grew Big and Lived for a Long Time

Scientists from the University of Vienna have been able to determine the approximate age and to estimate the rate of growth of an extinct species of shark that lived around 85 million years ago.  In addition, the researchers, writing in the open access on-line journal PLOS One, have estimated that this ammonite crunching fish could have been in excess of seven metres in length, but even though it was a giant, this shark was not yet fully mature and still had some growing to do.

Much of what we know about prehistoric sharks comes from studies of their fossilised teeth.  However, apart from providing indications on size, taxonomy and potential diet, these teeth do not provide a great deal of information about the life and the age of the individual.  In contrast, the calcified vertebrae of elasmobranchs (sharks, skates and rays), specifically the centra, yield important information about ecological and biological traits.  Two fossil shark vertebrae assigned to the genus Ptychodus found in northern Spain, have enabled researchers to gain valuable information on the life of a single individual animal that lived during the Late Cretaceous.

Site Photographs of the Shark Vertebrae

Picture credit:  K. Oppermann

A Shark from Northern Spain

The fossil material consists of a portion of the spine representing five articulated and several disarticulated vertebral centra from a single animal.  The fossils were found in Upper Cretaceous strata around six miles west of the town of Santander in northern Spain, from a limestone exposure close to the village of Soto de la Marina.

The extensive marine sediments document much of the Late Cretaceous – ranging from early Santonian through to Maastrichtian-aged deposits.  The shark fossils come a bedding plane representing the earliest Santonian (circa 85 million years ago).  Although no teeth were found in association with the fossil material, the scientists have referred this material to the Ptychodus genus.  A relatively common and widespread genus that specialised in eating hard-shelled animals such as shellfish and ammonites (duraphagous diet).

Calculating the Size of the Prehistoric Shark

Previous research had shown a link between the total length attained for several living shark species and the diameter of the vertebral centra.  The linear regression used to calculate potential length was applied to these fossils and the scientists concluded that the shark was between 4.3 to 7.07 metres in length.

Estimating the Size of the Ptychodus spp.

Picture credit: Patrick L. Jambura (University of Vienna)

Intriguingly, the centra of sharks also preserve evidence of growth rate, from which an age range can be deduced, just as the rings on a tree stump can provide an indication of the tree’s age.  An analysis of the centra from two fossils indicated that this shark was around thirty years old when it died, quite an age for a shark, although what age some sharks species alive today can live to remains unknown.  Based on this study, the researchers propose that ptychodontid sharks grew very slowly, matured very late, but also showed high longevity and had the potential to reach huge body sizes.

Calcification Pattern on the Centra Can Provide an Indication of Growth Rate and Age

Picture credit: PLOS One (Jambura and Kriwet)

The scientific paper: “Articulated remains of the extinct shark Ptychodus (Elasmobranchii, Ptychodontidae) from the Upper Cretaceous of Spain provide insights into gigantism, growth rate and life history of ptychodontid sharks” by Patrick L. Jambura and Jürgen Kriwet published in PLOS One.

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