Neuroanatomy of the abelisaurid theropod Viavenator exxoni

Viavenator exxoni, Museo Municipal Argentino Urquiza

The Abelisauridae represents the best-known carnivorous dinosaur group from Gondwana. Their fossil remains have been recovered in Argentina, Brazil, Morocco, Niger, Libya, Madagascar, India, and France. The group was erected by Jose Bonaparte with the description of  Abelisaurus Comahuensis. These theropods exhibit spectacular cranial ornamentation in the form of horns and spikes and strongly reduced forelimbs and hands. In South America, braincase remains are known for Carnotaurus sastrei, Abelisaurus comahuensis, Aucasaurus garridoi, Ekrixinatosaurus novasi, Skorpiovenator bustingorryi, Eoabelisaurus and Viavenator exxoni.

The holotype of Viavenator exxoni (MAU-Pv-LI-530) was found in the outcrops of the Bajo de la Carpa Formation (Santonian, Upper Cretaceous), northwestern Patagonia, Argentina. Cranial elements of this specimen include the complete neurocranium: frontals, parietals, sphenethmoids, orbitosphenoids, laterosphenoids, prootics, opisthotics, supraoccipital, exoccipitals, basioccipital, parasphenoids and basisphenoids. The cranial endocast of Viavenator measures 157.7 mm from the olfactory bulbs to the foramen magnum, with a volume of approximately 141.6 cm3. The general shape of cranial endocast is elongate and narrow, similar to Aucasaurus and Majungasaurus. The widest part of the cranial endocast of Viavenator is at the level of the cerebral hemispheres. Four blood vessel foramina are recognized in the braincase: the caudal middle cerebral vein, the rostral middle cerebral vein, the cerebral internal carotid artery and the sphenoid artery.

Figure 1. Rendering of the type braincase of Viavenator exxoni (MAU-Pv-LI-530) in dorsal (A,B), and right lateral (C,D) view. Adapted from Carabajal y Filippi, 2017.

The forebrain of Viavenator include the olfactory tracts and olfactory bulbs, the cerebral hemispheres, optic nerves, the infundibular stalk, and the pituitary body. The CT scans show that the olfatory tracts are undivided. The olfactory bulbs are oval and are separated by a median septum at the anterior region of the sphenethmoids. The optic lobes are not clearly defined. The visible features of the hindbrain in the cranial endocast include the cerebellum, medulla oblongata, and cranial nerves V–XII. The cerebellum is not clearly expanded in the endocast; however, the floccular process of the cerebellum is well defined. The general morphology of both, brain and inner ear of Viavenator is markedly similar to that of Aucasaurus.
Neurosensorial capabilities of extinct animals can be inferred in part based on the relative development of certain regions of the brain. The flocculus of the cerebellum plays a role in coordinate eye movements, and tends to be enlarged in taxa that rely on quick movements of the head and the body. The flocculus of Viavenator is particularly large compared with Majungasaurus, suggesting that Viavenator relied more on quick movements of the head and sophisticated gaze stabilization mechanisms than the African form. The dimensions of the auditory sensory epithelium of Viavenator is similar to Majungasaurus, suggesting that they had similar hearing capabilities. In large dinosaurs, hearing was restricted to low frequencies with high frequency limit below 3 kHz.

References:

Paulina-Carabajal, A., Filippi, L., Neuroanatomy of the abelisaurid theropod Viavenator: The most complete reconstruction of a cranial endocast and inner ear for a South American representative of the clade, Cretaceous Research (2017), doi: 10.1016/j.cretres.2017.06.013

Leonardo S. Filippi, Ariel H. Méndez, Rubén D. Juárez Valieri and Alberto C. Garrido (2016). «A new brachyrostran with hypertrophied axial structures reveals an unexpected radiation of latest Cretaceous abelisaurids». Cretaceous Research 61: 209-219. doi:10.1016/j.cretres.2015.12.018

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Tilly Edinger vs. the nazis.

Tilly Edinger (Photo,Museum of Comparative Zoology, Harvard University, Cambridge, MA)

“Tilly” Edinger was born on November 13, 1897 in Frankfurt, Germany. She was the youngest daughter of the eminent neurologist Ludwig Edinger and Dora Goldschmidt, a leading social advocate and activist. In 1914, her father became the first Chair of Neurology in Germany, at the newly founded University of Frankfurt. He encouraged her to take science courses at the Universities of Heidelberg, Frankfurt, and Munich. Her research at Frankfurt was directed by Fritz Drevermann, director of the Senckenberg Museum. After her graduation in 1921, Edinger worked as an assistant in the Geological Institute of Frankfurt University. In 1927, she was  named Curator of Fossil Vertebrates at the Senckenberg. At that time, she had no colleagues in vertebrate paleontology in Frankfurt with the exception of Drevermann. She described the positive and negative aspects of that environment in a letter addressed to A. S. Romer: “all fossil vertebrates [at the Senckenberg Museum] are entirely at my disposition: nobody else is interested in them . . . On the other hand, this means that I am almost autodidact”. 

Among her early projects were descriptions the endocranial casts of Mesozoic marine reptiles, pterosaurs and Archaeopteryx.  In 1929,  she published Die fossilen Gehirne (Fossil Brains), the book that established Edinger’s membership in the German and international paleontological communities. This work would serve as the major scientific support for her wartime immigration to the United States.

Senckenberg Naturmuseum (Senckenberg Museum of Natural History)

After the death of German President Paul von Hindenburg on August 2, 1934, Chancellor Adolf Hitler became Führer of Germany. In the months following Hitler’s ascension to the power, the Nazis took control of all of the nation institutions. The universities were not excepted. Soon, Jewish professors were dismissed, arrested, or simply disappeared. At the time, Tilly Edinger was working  as curator of fossil vertebrates at the Senckenberg Museum of Natural History in Frankfurt, so the influence of the new rules on her professional life was slower than on many other persons of Jewish descent because the Senckenberg was a private institution, and her position there was unsalaried. She continued working at the Museum thanks to protective actions of Rudolf Richter, the invertebrate paleontologist who had succeeded Drevermann at the Senckenberg.

Although urged by friends to leave the country, she chose to stay, as did their brother, Friedrich, who later (1942) became a victim of the Holocaust. But, on the night of 9–10 November 1938, her paleontological career in Germany ended.  Nearly 100 Jews were killed and thousands were imprisoned in the infamous “Kristallnacht” (Night of the Broken Glass). Decided to leave Germany as soon as possible, she wrote to her childhood classmate Lucie Jessner, a psychiatrist who had immigrated first to Switzerland in 1933 and then to the United States in early 1938. Jessner contacted the eminent Harvard paleontologist Alfred S. Romer (1884–1973), writing: “My friend—Dr. Tilly Edinger, paleontologist in Frankfurt am Main, Germany—wants me to ask you about different matters, very important for her. She believes you might know her name by several of her papers and you might be friendly enough to give me the opportunity to speak with you”

Interior of Berlin’s Fasanenstrasse Synagogue, opened in 1912, after it was set on fire during Kristallnacht on November 9, 1938

With the positive response from Romer, Edinger applied for an American visa at the American Consulate in Stuttgart on 1 August 1938. Forced to look for another, short-term solution, she contacted Philipp Schwartz, a former pathology professor at the University of Frankfurt who had established the Notgemeinschaft Deutscher Wissenschaftler im Ausland (Emergency Association of German Scientists in Exile), a society dedicated to helping scientific refugees from Nazi Germany. Waiting for a solution, she wrote to Rudolf Richter to thank him for his supportive testimonial. She shared her conviction that “One way (England) or the other (United States), fossil vertebrates will save me”. 

Thanks to her pioneering works and the contacts she made from a previous trip to London in 1926, Edinger emigrated to England in May 1939. She started working at the British Museum of Natural History, alternately translating texts and working on her own paleoneurological projects. She described her life in London as considerably freer than in Germany: “It sounds funny, to one who was ‘at home’ not allowed to enter even an open museum, or a cinema, or a café, to apply the word ‘restrictions’ anywhere in the beautifully free life I am leading here”

Tilly Edinger and colleagues at the Museum of Comparative Zoology. Sitting left to right: Tilly Edinger, Harry B. Whittington, Ruth Norton, Alfred S. Romer, Nelda Wright, and Richard van Frank. Standing left to right: Arnold D. Lewis, Ernest E.Williams, Bryan Patterson, Stanley J. Olsen, and Donald Baird. (Photo: David Roberts, from Buchholtz, 2001)

In 1940, with the support of Alfred S. Romer, she moved to Massachusetts to take a position at the Harvard Museum of Comparative Zoology. By the early 1950s, she was not only the major contributor to the field of paleoneurology but also the mentor to a younger generation that was following in her footsteps. She received several honorary doctorates for her achievements, including Wellesley College (1950), the University of Giessen (1957), and the University of Frankfurt  (1964). She was elected president of SVP in 1963. Her last book: “Paleoneurology 1804-1966. An annotated bibliography”, was completed by several of her colleagues and is considered the necessary starting point for any project in paleoneurology.

 

References:

Buchholtz, Emily A.; Seyfarth, Ernst-August (August 2001), “The Study of “Fossil Brains”: Tilly Edinger (1897–1967) and the Beginnings of Paleoneurology”, Bioscience 51 (8)

Susan Turner, Cynthia V. Burek and Richard T. J. Moody, Forgotten women in an extinct saurian (man’s) world, Geological Society, London, Special Publications 2010, v. 343, p. 111-153

 

 

Fossilized dinosaur brain tissue identified

Computer animation of a fossilized dinosaur brain (Credit: University of Manchester)

Computer animation of a fossilized dinosaur brain (Credit: University of Manchester)

Our knowledge of dinosaurian braincases and the structure of their endocranial cavities has a surprisingly long history. The first well-preserved braincase (NHMUK R2501) was found almost 150 years ago in the Isle of Wight and was described as probably belonging to Iguanodon. In 1897, Charles William Andrews – using the same specimen – suggested that dinosaurian brains, and in particular their lobes and surface convolutions, were not closely pressed against the cranial wall. Almost sixty years later, John Ostrom published a study on the anatomy of the hadrosaurian dinosaurs of North America and reinforced the general opinion that they had brains that were not packed tightly within the braincase. Previously, Alfred Romer observed that the interior walls of reptile braincases reflect the shape of the brain at an early state of its development. Now, a team of paleontologists from the University of Cambridge and the University of Western Australia uncovered the first fossilized brain tissue from a dinosaur.

The extraordinary specimen is likely to have belonged to a species related to Iguanodon, which lived around 133 million years ago. It was found in 2004 by fossil hunter Jamie Hiscocks, near Bexhill in Sussex. Fossilized footprints and trackways of Iguanodon-like ornithopods were found at a similar stratigraphic level.

Images of (a) the Bexhill iguanodontian natural endocast specimen and (b) a computed tomography. Scale bar: 10 mm (From Brasier et al., 2016)

Images of (a) the Bexhill iguanodontian natural endocast specimen and (b) a computed tomography. Scale bar: 10 mm (From Brasier et al., 2016)

The natural cranial endocast was unusually well preserved along its dorsolateral flanks, corresponding to the approximate position of the cerebellum. A scanning electron microscopy (SEM) revealed detailed structures, interpreted as meningeal fabrics, blood vessels and potentially superficial cortical tissues, which have been replaced by calcium phosphate or moulded by microcrystalline iron carbonate. The meningeal structures show similarities with those seen in crocodiles and birds. The areas occupied by the forebrain lobes and hypothalamus were well developed, so it’s reasonable to suppose that iguanodontian dinosaurs of this type had moderately complex behaviour similar to modern crocodilians.

To preserve soft tissue as phosphate is necessary a locally anoxic environment to promote bacterially mediated mineralization. Under freshwater conditions, eutrophication adds phosphate to the water column in the form of a phosphoric acid series that reduce the pH of the water, rapidly fixing soft tissues, and dissolving the surrounding mineralized tissues. As result, the soft tissues associated with the brain could have been preserved and cast prior to complete burial by sediment (Brasier et al., 2016).

References:

Martin D. Brasier et al.’ Remarkable preservation of brain tissues in an Early Cretaceous iguanodontian dinosaur.’ Earth System Evolution and Early Life: a Celebration of the Work of Martin Brasier. Geological Society, London, Special Publications, 448. (2016). DOI: 10.1144/SP448.3
Ostrom, J.H. 1961. Cranial anatomy of the hadrosaurian dinosaurs of North America. Bulletin of the American Museum of Natural History, 122, 35–196