Saturday, April 13, 2013

Devonian Tetrapod Fossils Link People to the Seas

Exploring Red Hill, Pennsylvania, and the First North American Tetrapod Discovery

This story I wrote appeared in the Paleontograph last year. I thought it especially appropriate to this blog because it deals with the discovery of the first North American tetrapod, a fish with fins becoming legs, a key product of evolution that links us with fish in the most intimate way.
Compared to other places we have searched, the Red Hill site yielded few fossils harder to work for. Situated in Clinton County, Pennsylvania, adjacent to the West Branch Susquehanna River, we hammered and chiseled, carefully extracting sedimentary sections, for relatively little evidence of late Devonian flora and fauna while light drizzle glazed red mudstone with September temperatures in the low 50’s. My family’s best find was a fish scale about three fourths of an inch diameter, almost certainly an instance of the large Hyneria predator. Other members of New York Paleontological Society found similar scales, pieces of plant stems, and a large section of fish vertebrae along the impressive, red-toned highway cut. But the scarcity of fossil finds paled in comparison to the importance of the rock we worked upon.
          By invitation from Douglas Rowe, who stewards the site in conjunction with Ted Daeschler of The Academy of Natural Sciences, Philadelphia, Curator of Vertebrate Zoology, the group traveled to north-central Pennsylvania in 2009 to collect, then stay in nearby Renovo and Hyner hotels for the night and resume collecting in the morning. The mood was somber as the weather and arrival of the fall season coupled with this fairly isolated region of Pennsylvania, but everyone seemed to feel pleased to be treated the opportunity with legendary Doug Rowe. This site is restricted to invitation only, and significant finds are released to Rowe and Daeschler, but Hyneria scales, isolated vertebra, plant matter, and possibly other minor finds were ours to keep.  
          Having finished collecting together late in the afternoon the day of our arrival, we caravanned to Rowe’s local museum, an enormous collection of fossils including some of the first North American tetrapod finds at Red Hill. Douglas Rowe is credited with Ted Daeschler for the very first North American tetrapod discovery in the early 1990’s at Red Hill. By synchronicity of interest and endeavor, Ted Daeschler happened upon Rowe pursuing his hobby at about this time along the road cut near Hyner and Renovo, deeply absorbed in both his authentic ability and the significance of this exposure of the Catskill Formation. Rowe has since received the 2007 Harrell L. Strimple Award for contributions to paleontology. One of two species of tetrapods discovered here, Densignathus rowei, is named after him.
          Tetrapods are extremely rare finds along the one kilometer Red Hill site; usually a shoulder piece or jaw is found rather than complete skeleton. The predominantly red mudstone is a deep deposit from a wide lowland river bed and flood plain of the Catskill Formation, which emptied into the inland Catskill Sea having flowed north and west from highlands. The tropical or sub-tropical climate produced a flourishing of plant life, and remains often found in the much less frequent green sandstone present along the cut suggests the ancient presence of ponds on the flood plain.
          Red Hill is one instance conveniently exposed by highway construction of a larger unit of like rivers forming the Catskill Delta produced by erosion of the Acadian Orogeny—mountains that lay to the south and east. Alluvial deposits extend from southeast New York, through Pennsylvania, Maryland, West Virginia, and northwest Virginia. Marine deposits associated are to the west into Ohio, and southward into Tennessee. The late Devonian continent of Euramerica, 365-370 million years ago, was distinctly characterized by the inland sea, and no doubt fish forming appendages to venture upon land is the most important value we encounter from that time.    

Matt Litton chisels sedimentary stone, eventually finding large fish scale (Hyneria) fossils a full inch across, 365-370 million years old.

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