BlueBeach – A walk back in time…

Around 370-362 million years ago there were fish-like critters with lungs. By 350 million years ago, tetrapods were the first known land animals, and they became fairly successful. However, during the deposition of early BlueBeach layers, there seems to be ~ 22 million years of time missing ( called Romer’s Gap – after the palaeontologist who recognized it.) What were the tetrapods doing? How were they evolving?

The early tetrapods were the first vertebrates to truly walk the land. Before tetrapods existed, vertebrates were all confined to living in aquatic habitats. The tetrapods began their conquest of land in the Paleozoic around 360 million years ago. Tetrapods are a name that we have given to anything with four feet (tetra=four, pod=feet). Therefore all land dwelling vertebrates can be considered tetrapods. However, when discussing the EARLY tetrapods, we are usually discussing very primitive groups that have none of the specializations of their living descendants: amphibians, mammals, and reptiles (including birds). Dendrerpeton, a common fossil of Joggins, Nova Scotia, is an example of an early tetrapod.

/ The tetrapod at left is an anthracosaur called Seymouria, from the UCMP collections. It is from North America, and is thought to be from the Permian period (between 286-248 million years ago!). It was previously thought to be related to amniotes, but recent studies suggest that it is a stem-tetrapod.

The pelvic specimen of Watchuria found at BlueBeach is the oldest and best sample known, and considered to be one of the top most exciting fossil finds in the world! Watchuria represents a very important group of tetrapods, which could be a key to understanding early sea-to-land evolution.

Tetrapod footprints are quite abundant at BlueBeach, although not many are particularly well-preserved. The BlueBeach museum now has the oldest (earliest) footprint collection in the world from one area. Most tracks and track-ways have between 3 – 7 toes in the footprints. The less toes, the more evolved the organism. In many cases, we see the presence of “underprints” – only the deepest pressure part of the track remains as erosion has removed the upper sections of rock.

The Lower Carboniferous is a very messy period of time as far as fossils are concerned – many missing “puzzle pieces” and some seemingly are “extras”! Since the BlueBeach area was once covered under a shallow warm sea, there are many fossils of paleoniscids (“ray-finned fishes”), which later evolved into such bony fish as herring, salmon, and trout. The rhizodonts (“lobe-finned fishes”) are larger animals related to tetrapods, but presently they are not well understood at all. They are a puzzle, as they can be up to 5 m in length here in Nova Scotia, yet up to 9 m long in Scotland!

William Dawson (1868) had originally collected jaw fragments and other fossil evidence as part of his work in trying to determine what organisms used to live here. One of the scales and teeth which he discovered so long ago are now recognized as a new species of rhizodont found at BlueBeach. These rhizodonts are the most primitive known, and had a different method of chomping down on prey. The jaw had a flexing action which could change the way of biting, allowing the teeth to hook and then tear. They were called the “jaws of annihilation”. There are only four sites world-wide that have these species, and three of them have been discovered in the last 15 years. Of all the specimens known, 9 of them are from BlueBeach!

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