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Kerste Milik
This Shark Week, let's celebrate the amazing work of paleontologists who continue to piece together the long and fascinating story of sharks' past.
Sharks have been around for over 400 million years, long before the dinosaurs, and we're still learning more every day about their impressive history.
From a 20-meter megalodon to an ancient shark nursery, here’s our roundup of all the biggest recent shark discoveries published here in Palaeontologia Electronica, all of which are open-access papers, always free for anyone to read!
It was a rough-skinned leviathan of biblical proportions. An epic fish tale to end all fish tales. A star of the silver screen. A true monster of the deep. Or was it? Despite megalodon (Otodus megalodon) being cemented in the popular imagination as the most massive shark of all time, a gargantuan set of jaws strapped onto a nuclear submarine, concrete details about the animal’s actual size are shrouded by the depths of time and poor preservation. Sharks, unlike bony fish and land-dwelling vertebrates, do not possess an ossified skeleton. Instead, shark bodies are supported by cartilaginous (made of cartilage) skeletons - a skeleton to be sure, but not one that preserves nearly as well as calcium-rich bones as one finds in other fish, amphibians, mammals, birds, and reptiles. As a consequence of this skeletal arrangement, whole body fossils of prehistoric sharks are exceedingly rare. Many species are known only from body elements that do preserve, mainly teeth. Megalodon is one such species. As of the writing of this blog, no whole body fossils of Otodus megalodon are known to science.
Small creatures can often provide big insights into past worlds. A recent paper published in Palaeontologia Electronica describes ten fossil Odonata (dragonflies and their relatives) wings from the Oligocene palaeolake Enspel. These wings, along with several well-preserved naiads (larval dragonflies), help paint a picture of a vibrant,
Figure 1. Nel et al. 2021 used the venation in wings such as these to identify different subgroups within Odonata. and buzzing, lost world in what is today southwestern Germany.
The palaeolake Enspel, according to André Nel, one of the researchers on the study, was “a freshwater lake with water of rather good quality, oligotrophic, high oxygen level probably, with a rich aquatic fauna, under a climate warmer than today, thus with a rich entomofauna.”
Wandering through a museum gallery can be a powerful experience. Walking under towering sauropod dinosaurs and peering through glass display cases at miniscule but immaculately detailed fossil fishes, one cannot help but catch glimpses of the prehistoric past. Exploring a museum collections room can be a similar experience. Drawers upon drawers of fossil material line aisles upon aisles of cabinets, all meticulously sorted and labelled. It is easy to think that the whole story of life on this planet resides within that building. While it is tempting to think that plants, animals, and fossils housed in a museum collection or on display represent a perfect sampling of “everything there” and present a one-to-one picture of what that time and place were really like, this is rarely the case. There are many reasons the fossil record is not a complete picture of ancient life, from animals not fossilizing to fossils being destroyed long before the first humans walked the Earth. It is perhaps then most frustrating when it is our own unconscious biases and foibles that distort our view of prehistory. A recent study in Palaeontologia Electronica uses the Cambrian Spence Shale Lagerstätte as a case study to dig into human-derived biases and how big of an impact they have on the way we study prehistoric life.
Caves are time capsules to the recent past. Tucked away beneath the surface of the Earth, fossils found in caves are not exposed to the same weathering and erosional forces as surface fossils. A surprisingly rich fossil deposit in Cueva de los Nesofontes in northwest Cuba sheds a good deal of light on the Holocene of Cuba – a poorly understood period of the island’s faunal history. A recent study published in Palaeontologia Electronica explores this deposit using stratigraphy, stable isotope analysis, and radiocarbon dating to shed light on this poorly understood time and place. In doing so, the researchers uncover a world that is younger and richer than they had previously imagined.
Without a skeleton or a hard shell, an animal’s chances of becoming a fossil are very slim. But under the right conditions, even soft-bodied animals like insects and spiders can be fossilized. A recent paper in Palaeontologia Electronica describes several Eocene spider fossils that were remarkably well preserved, including two new species.
Kerste Milik
Spinosaur teeth used in the study. Like all reptiles, dinosaurs constantly replaced their teeth.
A recent study published in Palaeontologia Electronica finds spinosaurid dinosaurs regrew their teeth unusually frequently, giving new insight into the dinosaurs’ dietary habits and explaining some puzzling phenomena in the fossil record.
Spinosaurs, the family of dinosaurs including the famous Spinosaurus, were remarkable creatures, from their enormous size to their crocodile-like skulls to the iconic sail on their backs. Like all reptiles, these dinosaurs had constant tooth replacement. This means that like humans, dinosaurs lost their teeth and they got replaced with new ones. However, instead of losing only one set of “baby teeth,” the dinosaurs continued losing and replacing teeth constantly throughout their lives, just like sharks and many other living creatures.
Kerste Milik
In a museum filled with towering dinosaurs, six small trilobites tell a big story. Paleontologists Russell Bicknell and Brayden Holland from University of New England, NSW documented evidence of injuries on trilobite fossils at the Royal Tyrrell Museum of Paleontology in Alberta, Canada, providing clues about predator-prey relationships in the Cambrian Period.
Trilobites were one of the oldest groups of arthropods—animals with exoskeletons and joint-legs, that includes insects and crustaceans. “A trilobite kind of looks like a slater (an isopod),” said Dr. Bicknell, “but has an exoskeleton that is made out of calcium carbonate, literal rock! And often they have a lot more spines than modern day isopods.”
Modern paleontology is exciting stuff. Once upon a time paleontology largely consisted of a team of dusty professors and college students baking in the summer heat as they carefully (and sometimes not so carefully) pried fossil bones, shells, and traces from their rocky tombs. It was grueling and unforgiving work. Still in its infancy, 19th and early 20th Century paleontology concerned itself with broad questions, e.g. “What is this animal?”, “What is it related to?”, “When did it live?”, “How big was it?” While some paleontology is still conducted this way (it certainly is in popular media), modern tools now allow paleontologists and other researchers to ask and answer questions they never dreamed would be possible only a few short decades ago.
Kerste Milik
In a July 2020 study in Palaeontologia Electronica, paleontologist Adiël A. Klompmaker and colleagues identified several Mesozoic crab specimens from sponge and coral-associated limestones in Europe. The researchers described six new taxa, reassigned several others, and documented some spectacular finds.