The lifestyle of spinosaurids has been a topic of intense debate since important new skeletal parts were uncovered. Spinosaurus aegyptius Different lifestyles of this species have been proposed in the literature. Some claim that they were more or less semi-aquatic, hunting fish from the edges of bodies of water or by walking or swimming on the surface. Others suggest that it was entirely aquatic and an underwater tracking predator.
A pair of animals that do things better than any animal that has ever evolved. Spinosaurus aegyptius About 95 million years ago, pterosaurs soared overhead on the northern coast of Africa and invaded nearby waters in search of prey. Image credit: Daniel Navarro.
Paleontologists generally agree that Spinosaurus aegyptius were fish-eaters, but how exactly these dinosaurs caught their prey is the subject of active debate, with some researchers suggesting that they hunted on the coast and others walked or swam in shallow water, and other researchers have suggested that it was an aquatic tracking predator.
One recent study used a fairly new statistical method called phylogenetic flexible discriminant analysis (pFDA) to analyze the density and proportion of organisms and supported the latter hypothesis. spinosaurus skeleton.
In a new study, University of Chicago professor Paul Sereno and colleagues critically evaluated the methods of previous research and identified significant flaws.
“spinosaurusand its close relatives, are fascinating due to their unusual anatomical features, the rarity of specimens, and the fact that scientists
had not discovered bones in any parts of their bodies until very recently. they stated.
“Unlike other carnivorous dinosaurs, there is strong evidence that it lived near water and ate fish and other aquatic organisms.”
“This has caused a lot of controversy as to how it is done. spinosaurus It was alive—was it a fast-swimming predator chasing fish like a sea lion? Or maybe it’s a predator lurking at the water’s edge, grabbing at you with its clawed hands like a gigantic version of a brown bear chasing a salmon, or poking its head into the water like a seven-ton heron from hell. I wonder if it was? ”
The authors began by asking new questions about bone density, such as how to digitize thin sections, where to slice through the femur and ribs, and whether to include bones from multiple individuals.
Some modern aquatic mammals, like manatees, have dense bones that bulge to help them stay underwater, like a scuba diver’s weight belt.
Large land animals such as elephants and dinosaurs also have dense bones to support their increased weight.
most modern birds and many dinosaurs spinosaurus Air sacs are attached to the inside of the lungs and bones and act like a life jacket to prevent submersion.
Assessing the aquatic abilities of extinct species such as spinosaurus All these factors must be considered.
Given the complexity of understanding the meaning of bone density, paleontologists reevaluated how statistical methods used in previous studies were applied to support the following claims: . spinosaurus It was a deep diver.
pFDA's approach is similar to machine learning, training classification algorithms based on groups of species whose lifestyles are well understood.
In principle, researchers could use algorithms to estimate the likelihood of the existence of poorly understood species such as: spinosaurus classified into some behavioral group.
“But in reality, there are challenges that need to be overcome,” said Intellectual Ventures researcher Nathan Myhrvold.
“Unfortunately, this technique doesn’t work well unless you have a large amount of data and do apples-to-apples comparisons to ensure that the data meets certain statistical assumptions.”
“None of these requirements were met in the previous study, so the results did not stand up to review.”
This new paper should help paleontologists understand the pitfalls of pFDA and other types of extensive statistical analysis and how to avoid them.
Researchers show that it is important to use consistent and objective criteria when deciding which species to include or exclude, and how to categorize their behavior .
The results of this study also demonstrate the importance of considering measurement error and individual differences when assessing bone mineral density.
“We think spinosaurus“As one of the largest predators to have ever evolved, this animal needed extra bone strength to support its weight on its relatively short hind legs,” Professor Sereno said.
“spinosaurus They could walk in channels more than 6 feet deep without floating, and could use their claws and jaws to ambush fish of any size, even while keeping their toes firmly planted in the mud. I stayed. ”
of study It was published in the magazine PLoS ONE.
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NP Myhrvold other. 2024. Diving dinosaur? Considerations regarding the use of bone density and pFDA to infer lifestyle. PLoS ONE 19 (3): e0298957; doi: 10.1371/journal.pone.0298957
