Megalodon

[Grey]

Really large teeth may not be so hard to get, I have contemplated the idea to suggest the authors of the respective methods to test on teeth corresponding to 13-15 m individuals.

Who knows, maybe some of the really large mega would show lower nitrogen levels as they could forage on some of the 15 m + balaenopterids, even though those have only been recorded from Peru so far.

I don't know much yet but apparently Livyatan was probably not the only really large carnivorous cetacean in this region.

[Grey]

The extinct shark Otodus megalodon was a transoceanic superpredator: Inferences from 3D modeling

www.science.org/doi/10.1126/sciadv.abm9424

theconversation.com/ancient-megalodon-super-predators-could-swallow-a-great-white-shark-whole-new-model-reveals-188749

[Infinity Blade]

[Grey]

A Shear-Compression Fracture

A Miocene cetacean vertebra showing a partially healed longitudinal shear-compression fracture, possibly the result of domoic acid toxicity or failed predation

Stephen J. Godfrey and Brian L. Beatty



palaeo-electronica.org/content/2022/3694-a-shear-compression-fracture

[Infinity Blade]

Endothermic physiology of extinct megatooth sharks

Significance

Otodus megalodon was a gigantic shark that went extinct around 3.6 Mya. It could grow to the enormous size of at least 15 m long, making it one of the largest apex marine predators since the Mesozoic. Here, we test hypotheses relating to its extinction by providing quantitative estimates of its body temperature, thereby constraining its thermal physiology. We found that O. megalodon had body temperatures significantly elevated compared to other sharks, consistent with it having a degree of internal heat production as modern warm-blooded (endothermic) animals do. High metabolic costs associated with having at least partial endothermy may have contributed to its vulnerability to extinction compared to other shark species that persist until this day.


Abstract

The evolution of the extinct megatooth shark, Otodus megalodon, and its close phylogenetic relatives remains enigmatic. A central question persists regarding the thermophysiological origins of these large predatory sharks through geologic time, including whether O. megalodon was ectothermic or endothermic (including regional endothermy), and whether its thermophysiology could help to explain the iconic shark’s gigantism and eventual demise during the Pliocene. To address these uncertainties, we present unique geochemical evidence for thermoregulation in O. megalodon from both clumped isotope paleothermometry and phosphate oxygen isotopes. Our results show that O. megalodon had an overall warmer body temperature compared with its ambient environment and other coexisting shark species, providing quantitative and experimental support for recent biophysical modeling studies that suggest endothermy was one of the key drivers for gigantism in O. megalodon and other lamniform sharks. The gigantic body size with high metabolic costs of having high body temperatures may have contributed to the vulnerability of Otodus species to extinction when compared to other sympatric sharks that survived the Pliocene epoch.

www.pnas.org/doi/10.1073/pnas.2218153120

[Infinity Blade]

Tessellated calcified cartilage and placoid scales of the Neogene megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), offer new insights into its biology and the evolution of regional endothermy and gigantism in the otodontid clade

The late Neogene megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), is mostly known for its gigantic teeth and vertebrae. Re-examination of the rock matrix surrounding a previously described associated tooth set of O. megalodon from the upper Miocene of Japan resulted in the observation of numerous fragments of tessellated calcified cartilage and placoid scales. The morphology of each tessera and the arrangement of overall tessellated calcified cartilage are practically identical to those of extant chondrichthyans. Many placoid scales possess pronounced, rather broadly-spaced keels. A quantitative relationship between interkeel distances of keeled scales and reported cruising speeds across extant pelagic lamniforms and carcharhiniforms suggests that O. megalodon with a representative interkeel distance of ca. 100 µm was not a fast swimmer. We propose that O. megalodon was generally a slow cruising shark with occasional burst swimming for prey capture, where much of its metabolic heat through regional endothermy was possibly used to facilitate the digestion of large pieces of ingested meat as well as absorbing and processing nutrients. If so, the relative importance of the functional roles of regional endothermy possibly shifted from maintaining high cruising speeds to visceral food processing through the evolution towards gigantism in otodontids.

www.tandfonline.com/doi/full/10.1080/08912963.2023.2211597

[Infinity Blade]

Three-dimensional shape of natural riblets in the white shark: relationship between the denticle morphology and swimming speed of sharks

The ridges of the dermal denticles of migratory sharks have inspired riblets to reduce the frictional drag of a fluid. In particular, the dermal denticles of white sharks (Carcharodon carcharias) are characterized by a high middle ridge and low side ridges. The detailed morphology of their denticles and their variation along the body, however, have never been investigated. Moreover, the hydrodynamic function of high–low combinations of ridges is unknown. In this article, the ridge spacings and heights of the white shark denticles were three-dimensionally quantified using microfocus X-ray computed tomography. Then, the swimming speed at which the ridges would reduce drag was hydrodynamically calculated with a flat plate body model and previous riblet data. High ridges with a large spacing were found to effectively reduce drag at a migration speed of 2.3 m s−1, while adjacent high and low ridges with a small spacing reduced drag at a burst hunting speed of 5.1 m s−1. Moreover, the above hydrodynamic calculation method was also applied to the shortfin mako shark and an extinct giant shark (called megalodon) with known ridge spacings, resulting in the estimated hunting speeds of 10.5 m s−1 and 5.9 m s−1, respectively.

royalsocietypublishing.org/doi/abs/10.1098/rsif.2024.0063

[Infinity Blade]

A bit different from most content posted on our profiles, but here's a neat video summarizing the best available evidence regarding the biology of Otodus megalodon and its extinction.