We the Creatures | Saccorhytus

For hundreds of years we have theorized and discussed evolution. In a nutshell, we can assume that after the Big Bang, minuscule organisms formed which eventually evolved into tiny sea creatures, leading to land mammals and then humans. For decades, scientists have been searching for what they call LUCA (Last Universal Common Ancestor); small pieces of the puzzle to date us back further than primates.

Photograph of the Saccorhytus fossil and an artists' impression of the creature as it would have looked when it was alive. Credit: Jian Han (Northwest University, China) here...

Photograph of the Saccorhytus fossil and an artists' impression of the creature as it would have looked when it was alive. Credit: Jian Han (Northwest University, China)here...


Paleontologists have just discovered what appears to be the earliest know human ancestor, the Saccorhytus. The 540 million year-old fossil was found in sedimentary rock in Shaanxi, Central China. It is microscopic but well preserved, so detail was easily translated into an artistic rendering for a better idea of the creatures' characteristics.

We had to process enormous volumes of limestone – about three tonnes – to get to the fossils, but a steady stream of new finds allowed us to tackle some key questions: was this a very early echinoderm, or something even more primitive? The latter now seems to be the correct answer.
— Dr Jian Han, of Northwest University
 
(g), a ventral view of the body cones (bc), the mouth (M), and two circular pores (Bc1). Published by Simon Conway Morris/University of Cambridge

(g), a ventral view of the body cones (bc), the mouth (M), and two circular pores (Bc1). Published by Simon Conway Morris/University of Cambridge


This creature falls into the Deuterostome family, which is a broad range of species including 'vertebrates' or 'backboned animals'. Measuring in at roughly one millimeter, it is thought to have lived between grains of sand on the seabed.

Our team has notched up some important discoveries in the past, including the earliest fish and a remarkable variety of other early deuterostomes. Saccorhytus now gives us remarkable insights into the very first stages of the evolution of a group that led to the fish, and ultimately, to us.
— Degan Shu, from Northwest University in Xi'An, Shaanxi Province, where the fossils were found

Characteristics include a spine, large mouth and symmetrical definition. It would have been covered with a flexible but thin layer of skin and muscle, using contractions to move around much like an urchin. An interesting observation was the absence of an anus, suggesting that food went in and came out through the same orifice, its mouth. Conical formations on the body appear to be early stages of what we now know as gills with possible sensory structures.

 

Homologous similarity among vertebrate embryos

Homologous similarity among vertebrate embryos


Although we have only discovered one thousandth of a percent of estimated species on earth, this Saccorhytus creature is now the oldest known to have ties with humanity. 

Reference:  http://www.nature.com/nature/journal/vaop/ncurrent/full/nature21072.html

 

WildlifeThe Nile| culture