Evolution: first land animals (Evolution)

by David Turell , Monday, June 02, 2025, 18:51 (25 days ago) @ David Turell

Fill a gap:

https://www.sciencedaily.com/releases/2025/05/250529194648.htm

The fossils of ancient salamander-like creatures in Scotland are among the most well-"preserved examples of early stem tetrapods -- some of the first animals to make the transition from water to land. Thanks to new research, scientists believe that these creatures are 14 million years older than previously thought. The new age -- dating back to 346 million years ago -- adds to the significance of the find because it places the specimens in a mysterious hole in the fossil record called Romer's Gap.

***

"Garza took a risk when he embarked on his mission to date the ancient fossils using a geochemical technique called radiometric dating.

"That's because while geoscientists can use zircon crystals to determine how long ago a rock was formed, not all rock types are amenable to this type of analysis. And the site in Scotland where the fossils were discovered was near ancient volcanoes whose lava flows had long hardened into basalt rock, where zircons do not typically form. Fellow scientists warned Garza that chemically dating the rocks might be fruitless.

***

"In 1984, an amateur paleontologist in Scotland found a remarkable specimen: a nearly complete fossil of what looked to be a lizard or salamander. Rather small in size at 20 centimeters, it would turn out to be a crucial piece in the puzzle of animal evolution.

"This creature, called Westlothiana lizziae, is one of the earliest examples of a four-legged animal that had evolved from living underwater to dwelling on earth. It, and other stem tetrapods like it, are common ancestors of the amphibians, birds, reptiles and mammals that exist today, including humans.

***

"Garza X-rayed 11 of the rock samples at the Jackson School and was able to extract zircons from the rock surrounding six of the fossils. He then conducted uranium-lead laser dating on the zircons at the University of Houston to determine their oldest possible age.

***

"The more accurate, older maximum age of 346 million years is significant because it places the specimens in Romer's Gap. This is a time period from 360 to 345 million years ago where, for reasons scientists are not exactly sure of, very few fossils have been discovered. It is during this crucial point in history that water-dwelling fish took an evolutionary leap, growing lungs and four legs to become land animals. This is one of the most pivotal milestones in the history of animal evolution."

Comment: This finding satisfies dhw's wish for more fossil discoveries by filling a recognized gap in specimens. That is what is left to find, just specimens to fill recognized gaps in the fossil record. New, dramatic, theory changing discoveries are most unlikely.