126 — Live birth in the Devonian period

The Gogo Formation in Western Australia is a particularly well-preserved Devonian-era shallow-water reef: The site is notable for its consistent preservation of three-dimensional, soft tissue in its limestone. The limestone can be dissolved with acetic acid, leaving the 3D fossil behind.

Materpiscis attenboroughi is one animal discovered at the Gogo Formation using this method. M. attenboroughi is a ptyctodontid placoderm — an “armored fish” whose lineage has since gone extinct. This fossil is remarkable in that a smaller fossilized animal was found inside the M. attenboroughi: Long et al discovered that this smaller animal was in fact an embryonic offspring.

At the time of its discovery, this made M. attenboroughi — alive in the Devonian period 380 million years ago — the oldest known instance of viviparity in the vertebrate family tree.

This discovery holds such importantance because it teaches us two important things about vertebrate evolution: First, it changes our understanding of when live birth arose as a vertebrate trait by hundreds of millions of years: This discovery is a paradigm shift in the history of viviparity. Second, it demonstrates that the single fish remained in utero until it was fully formed and likely able to fend for itself: This means that the offspring likely required minimal care and attention after birth.