Testing the aquatic spinosaurid hypothesis

This is the only photographic proof of German researcher Ernst Stromer’s discovery of Spinosaurus. Image from the Washington University in St. Louis

The Spinosauridae is a specialized group of large tetanuran theropods known from the Berriasian to the Cenomanian of Africa, South America, Europe and Asia. The group is characterised by a long, narrow skull, robust forelimbs with a hooked thumb claw, and tall neural spines forming a dorsal sail.  Spinosauridae has been divided in two clades Baryonychinae (including Suchomimus, Baryonyx and Cristatosaur), and Spinosaurinae. Baryonyx walkeri, described by Alan Charig and Angela Milner in 1983, is the oldest unquestionable spinosaurid. The ecology of the group has been debated since the original discovery of Spinosaurus aegyptiacus in 1911. Although Stromer’s original description of Spinosaurus was published in 1915, a more complete detailed picture of its anatomy, evolution, and biogeography only begun to emerge in recent decades with the discovery of a partial skeleton of a subadult individual of S. aegyptiacus in the Cretaceous Kem Kem beds of south-eastern Morocco. At the time of deposition, this part of Morocco was located on the southern margin of the Tethys Ocean and it was characterized by an extensive fluvial plain dominated by northward flowing rivers and terminating in broad deltaic systems on Tethys’ southern shores. The discovery of this new skeleton of Spinosaurus has challenged the paradigma about the restriction of non-avian dinosaurs to terrestrial environments. Previous paleo-histological studies suggested that Spinosauridae had a strong relationship with aquatic environment. Now, a new study published in Nature, indicates that they were aquatic specialists.

Osteohistology variation among the analysed spinosaurid taxa. From Fabbri et al., 2022

Since the works of Nopcsa and Heidsieck in 1934, it has been suggested that the secondary adaptation of tetrapods to an aquatic environment induced modifications of the inner architecture and histological characteristics of bones. Using femora and dorsal ribs to test the correlations between bone density and ecology of these animals, the team lead by Dr. Matteo Fabbri built a dataset of 291extinct and extant amniote species, including mammals, marine reptiles and birds.

Bone density is associated with buoyancy control. Many studies on avian microanatomy had already established a relationship between high bone compactness (i.e., considerable degree of osteosclerosis) and diving behavior. The presence of high bone density in Spinosaurus and Baryonyx supports the hypothesis that spinosaurids were aquatic specialists. Additionally, the highly specialized morphology of the Spinosaurus tail allowed it to function as a propulsive structure for aquatic locomotion. The anterior positioning of the center of mass within the ribcage may have also enhanced balance during aquatic movement. On the other hand, Suchomimus exhibits hollower bones and it was more adapted to a life hunting in shallow water.

References:

Fabbri, M., Navalón, G., Benson, R.B.J. et al. Subaqueous foraging among carnivorous dinosaurs. Nature (2022). https://doi.org/10.1038/s41586-022-04528-0

HONE, D. W. E. and HOLTZ, T. R. (2017), A Century of Spinosaurs – A Review and Revision of the Spinosauridae with Comments on Their Ecology. Acta Geologica Sinica, 91: 1120–1132. doi: 10.1111/1755-6724.13328

Ibrahim, N., Sereno, P. C., Dal Sasso, C., Maganuco, S., Fabbri, M., Martill, D. M., Zouhri, S., Myhrvold, N., Iurino, D. A. (2014). Semiaquatic adaptations in a giant predatory dinosaur. Science, 345(6204), 1613–1616. doi:10.1126/science.1258750 

Aureliano, T., Ghilardi, A.M., Buck, P.V., Fabbri, M., Samathi, A., Delcourt, R., Fernandes, M.A., Sander, M., Semi-aquatic adaptations in a spinosaur from the Lower Cretaceous of Brazil, Cretaceous Research (2018), doi: 10.1016/j.cretres.2018.04.024

First Triassic records of pterosaurs in the southern hemisphere.

Pachagnathus and Yelaphomte. Image credit: Jorge Blanco

Pterosaurs were the first flying vertebrates. Their reign extended to every continent and achieved high levels of morphologic and taxonomic diversity during the Mesozoic. The oldest-known pterosaurs appear in the fossil record about 219 million years ago. Most Triassic pterosaurs are small but already had a highly specialized body plan linked to their ability to fly: shoulder girdle with strongly posteroventrally enlarged coracoid braced with the sternum and laterally facing glenoid fossa; forelimb with pteroid bone and hypertrophied fourth digit supporting a membranous wing; and pelvic girdle with prepubic bone and strongly developed preacetabular process. By the Mid-Jurassic, pterosaurs had a worldwide distribution, but their known record is markedly biased toward the northern hemisphere. The description of two new specimens from Quebrada del Barro Formation in north-western Argentina are the first unequivocal Triassic records of pterosaurs in the southern hemisphere. Previous to this new work, the only record of a Triassic pterosaur in southern hemisphere was Faxinalipterus minima, from the Caturrita Formation in southern Brazil, although now is considered as a basal Ornithodira.

Pachagnathus benitoi, partial mandibular symphysis in right and left view. From Martinez et al., 2022

Yelaphomte praderioi was a small pterosaur. The holotype (PVSJ:914) is represented by a partial rostrum with the anterior part of both maxillae and palatine, and the posterior portion of both premaxillae. The highly fused bones of the rostrum may indicate its maturity and adult size. The generic name derived from the Allentiac language (spoken by the Huarpe) and means beast of the air, referring to the extreme pneumaticity of the rostrum of the new species and its capacity to flight. The specific name honors Angel Praderio, who discovered the new specimen.

Pachagnathus benitoi was a moderate-sized pterosaur. The holotype (PVSJ:1080) is a partial mandibular symphysis lacking anterior end, preserving one tooth and three alveoli from the the left side, and the roots of three teeth and two alveoli from the right side. The name comes from the words “Pacha” (Earth, in Aymara languaje) and “gnathus” (jaws, in Greek). The specific name honours Benito Leyes, who found the first fossils in Balde de Leyes.

 

References:

Martínez, R.N., Andres, B., Apaldetti, C. and Cerda, I.A. (2022), The dawn of the flying reptiles: first Triassic record in the southern hemisphere. Pap Palaeontol, 8: e1424.https://doi.org/10.1002/spp2.1424

Martínez, R.N., C. Apaldetti, G. Correa, C.E. Colombi, E. Fernández, P. Santi Malnis, A. Praderio, D. Abelín, L.G. Benegas, A. Aguilar-Cameo & O.A. Alcober. 2015. A new Late Triassic vertebrate assemblage from northwestern Argentina. Ameghiniana 52: 379–390.

Eunice Foote, climate change, and the Matilda Effect

Eunice Foote, née Newton (1819–1888), Photo credit: WSKU Public Radio News for Northeast Ohio

The birth of modern science was hostile to women’s participation. The world’s major academies of science were founded in the 17th century: the Royal Society of London (1662), the Paris Académie Royale des Sciences (1666), and the Berlin Akademie der Wissenschaften (1700), but women were not become members until the 20th century. Often, the work of women were invisibilized. In the 18th and 19th centuries women’s access to science was limited, and science was usually a ‘hobby’ for intelligent wealthy women. In 1993, science historian Margaret W. Rossiter coined the term “Matilda effect” to describe the bias against acknowledging the achievements of those women scientists. Some cases illustrating the Matilda effect include those of Agnes Pockels, Eunice Foote, Nettie Stevens, Lise Meitner, Rosalind Franklin, and Jocelyn Bell Burnell.

Eunice Foote’s paper in the American Journal of Science and Arts. Royal Society

Eunice Newton Foote was born on July 17, 1819, in Goshen, Connecticut. She published just two papers, in 1856 and 1857. In her first paper, “Circumstances affecting the heat of the sun’s rays,” she suggested that greater amounts of carbon dioxide (CO2) in the atmosphere would increase Earth’s temperature. That statement was made five years before John Tyndall demonstrated that gases such as methane and carbon dioxide absorbed infrared radiation, and could trap heat within the atmosphere. In a Scientific American article from 1856, which discusses the contribution of women to the advancement of science, it was suggested that Eunice Foote’s experiment, exposing tubes containing different gases to the sun, was designed to test the hypothesis that carbon dioxide concentrations in the atmosphere lead to global warming and can explain warm periods in the geologic past. The article also offers a glimpse of the early nineteenth century understanding of climate change in the geologic past.

Women and men who signed the Declaration of Sentiments at first Woman’s Rights Convention, July 19-20, 1848. From Wikimedia Commons.

Eunice Foote was also part of the women’s-rights movement. She and her husband, Elisha Foote, a judge, inventor, and mathematician, were part of the first woman’s rights convention. Along with Lucretia Mott, Elizabeth Cady Stanton and Frederick Douglas, they signed the Seneca Falls Declaration in 1848. Douglas described the document as the “grand movement for attaining the civil, social, political, and religious rights of women.”

Eunice Foote died on 30 September 1888. A summary of her work was published in the 1857 volume of Annual of Scientific Discovery by David A. Wells, who wrote: “Prof. Henry then read a paper by Mrs. Eunice Foote, prefacing it with a few words, to the effect that science was of no country and of no sex. The sphere of woman embraces not only the beautiful and the useful, but the true.”

 

References:

Foote, Eunice, 1856. Circumstances affecting the heat of the Sun’s rays: Art. XXXI, The American Journal of Science and Arts, 2nd Series, v. XXII/no. LXVI, November 1856, p. 382-383.https://ia800802.us.archive.org/4/items/mobot31753002152491/mobot31753002152491.pdf 

Rossiter, M. W. (1993). The Matthew Matilda Effect in Science. Social Studies of Science, 23(2), 325–341. http://www.jstor.org/stable/285482

Jackson, Roland. (2019). Eunice Foote, John Tyndall and a question of priority. Notes and Records: The Royal Society Journal of the History of Science, 0(0), 20180066. https://doi.org/10.1098/rsnr.2018.0066

Ortiz, J. D., & Jackson, R. (2020). Understanding Eunice Foote’s 1856 experiments: heat absorption by atmospheric gases. Notes and Records: The Royal Society Journal of the History of Science. doi:10.1098/rsnr.2020.0031

Scientific Ladies.—Experiments with Condensed Gases. (1856). Scientific American, 12(1), 5–5. http://www.jstor.org/stable/24947406