Millions of years ago, in the warm Pacific Ocean off the coast of Southern California, walrus species without tusks lived in abundance.
But in a new study, Cal State Fullerton paleontologists have identified three new species of walruses found in Orange County, and one of the new species has “half-dead”
The other two new species have no tusks, and all precede the evolution of the long iconic ivory tusks of the modern walrus, which lives in the cool Arctic.
The researchers described a total of 12 fossil walruses from Orange, Los Angeles and Santa Cruz counties, all estimated to be between 5 and 10 million years old. The fossils are of five species, with two of the three new species represented by males, females and juveniles.
Their research, which gives an idea of the evolution of the teeth and tusks of marine mammals, was published today in Journal of Vertebrate Paleontology.
Geology graduate Jacob Beaver and his research advisor, James F. Param, an associate professor of geology, are the authors of a study based on fossil skull samples.
Parham and Biewer worked with Jorge Velez-Juarbe, a marine mammal expert at the Los Angeles County Museum of Natural History who co-authored the article. Veles-Juarbe is a former postdoctoral fellow at Parkham’s laboratory and has collaborated on other CSUF fossil research projects. Param is a research associate at the museum that provides research opportunities for him and his students.
Researchers have teamed up to study and describe the anatomy of the specimens, most of which are part of the museum’s collection.
“Orange County is the most important area for fossil walruses in the world,” said Beaver, the first author of the paper to do research on his master’s thesis. “This study shows how walruses evolved with tusks.”
Extinct walrus species are named
Today there are only one walrus and its scientific name is Odoben.
For the new species found in Orange County, researchers named the semi-tusk walrus Osodobenus eodon, combining the words Oso and Odobenus. Another is named Pontolis kohnoi after Naoki Kohno, a fossil walrus researcher from Japan. Both of these fossils have been found in the Irvine, Lake Forest and Mission Viejo areas.
Osodobenus eodon and Pontolis kohnoi are also from the same geological rock layer as the 2018 study of Parham and his students from another new genus and species of washless walrus, Titanotaria orangensis, named after the titans of CSUF. These fossils have been found in Oso, a member of the Capistrano Formation, a geological formation near Lake Forest and Mission Viejo.
A third new species of walrus, Pontolis barroni, was found at Aliso Viejo, near Toll Road 73. It is named after John Barron, a retired researcher at the USGeological Survey and a global rock expert where the specimens were found, Param said.
The analysis of these specimens shows that fossil walrus teeth are more variable and complex than previously considered. Most of the new specimens precede the evolution of tusks, Param said.
“Osodobenus eodon is the most primitive walrus with tusk-like teeth,” Param said. “This new species demonstrates the important role of food ecology in the origin and early development of tusks.”
Beuer explained that his work focuses on better understanding the evolutionary history of the walrus in terms of its teeth.
“The importance of dental evolution is that it shows variability within and between walrus species. Scientists have suggested that you can identify certain species only on the basis of teeth, but we show how even individuals of the same species can have variability in their teeth. settings, ”said Beaver, who won a master’s degree in geology in 2019.
“Furthermore, everyone suggests that tusks are the most important teeth in walruses, but this study further highlights how tusks are a later addition to the history of walruses. Most species of walruses were fish-eating and adapted to fish rather than using suckers. feeding on molluscs like modern walruses. “
Biewer, now a paleontologist in the Modesto area, is also investigating whether climate change in the Pacific has affected ancient walruses. His work suggests that rising water temperatures have helped increase nutrients and planktonic life and played a role in the spread of walruses about 10 million years ago, which may have contributed to their diversity.
For the fossil walrus research project, geology graduate Jacob Beer spent hours in the lab measuring and describing walrus bones.
“I sat for many hours with a comfortable caliper, noting the lengths of my teeth and the width of my skulls, among many other measurements,” he said. “The description of the bones is much more thorough and thorough than it sounds. There are features that the bones of each walrus species have – the size, shape and number of teeth. I have recorded how the bones are different or similar to other extinct walrus species.”
Biewer, a paleontologist living in Modesto, noted that despite the pandemic, he and Parkham worked on scientific work with 300 miles of social distance.
Completing his first journal publication, based on his master’s work, and conducting a research project helped him understand the scientific methods and techniques he now uses in his career, where he observes construction sites for paleontological resources. He also teaches bachelor’s courses in geology at Cal State Stanislaus, where he received a bachelor’s degree in geology and is considering pursuing a doctorate.
“The experience I had in conducting this study, especially the presentations at national paleontological conferences, led to a great increase in my confidence in my scientific abilities,” Beuer said. “I attribute my time working with Dr. Param directly to the achievements of my current job, from the skills he imparted to the doors he helped open.”
Further evidence against the ancient theory of the “killer walrus”
Jacob N. Biewer et al., Insights into the dental evolution of walruses based on new fossil samples from California, Journal of Vertebrate Paleontology (2020). DOI: 10.1080 / 02724634.2020.1833896
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