WIKIMEDIA, KERESHThe diversity of penis features among amniote vertebrates has left evolutionary biologists with an unanswered question: Did male external genitalia evolve more than once? In a study published this week (October 28) in Biology Letters, researchers looked to embryos of an ancient amniote lineage, finding that they go through a developmental stage with a penis that’s conserved among other amniotes.
The subject of the study, a reptile called a tuatara, does not have a phallus as an adult. So looking at its development could lend insight into whether it experiences stages of genital growth common to other amniote lineages.
Given the endangered state of tuataras, the authors turned to Victorian-era slides of tuatara embryos housed at Harvard’s Museum of Comparative Zoology. “The slides had been in storage for most of the 20th century,” Thomas Sanger, a postdoc at the University of Florida who led the study, told Gizmodo. “So some slides had gone missing. They were also pretty dusty and beat up, and required some careful cleaning before I could photograph them. But for specimens that were over 100 years old, the histological quality was ...
