A new analysis of the fossils of several recently discovered juvenile Metoposaurus diagnosticus found in Krasiejów, Poland by Dorota Konietzko-Meier of the University of Opole in Poland and the University of Bonn, Germany, and P. Martin Sander also of the University of Bonn reported in the Sept. 2, 2013 edition of the Journal of Vertebrate Paleontology concludes the Triassic amphibian burrowed during the dry season.
Metoposaurus diagnosticus lived 230 million years ago. The amphibians grew to a length of ten feet and weighed 1,000 pounds when fully grown.
The newly discovered juvenile specimens are complete enough to define a flat head, broad flat front legs, and a large flat tail. The gross skeletal structure led the researchers to conjecture that the amphibian burrowed to survive the dry periods of climate during the Triassic.
An examination of the growth rings in the leg bones of the Metoposaurus diagnosticus displayed two distinct patterns. One broad band of rapid growth and one thin band of slow growth repeated in each of the specimens discovered that argues for burrowing during the dry season and rapid growth during the wet season. The specimens that were discovered were juveniles ranging in age from one to four years of age based on the number of repeated bone rings.
The researchers cannot assume that adults burrowed to avoid the dry season conditions but that assumption seems likely.