March 17, 2023

(public display, Cleveland Museum of Natural History, Cleveland, Ohio, USA)

After I blogged about students dressing up as blue sharks (Sharkansas) for the Kentucky basketball game (Arkansas lost by 9) I was interested to find an article in my local paper several days later about another extinct fish who was back in the news.  Dunkleosteus is an extinct genus of large arthrodire (armored and jawed) fish that existed during the Late Devonian period, or about 382–358 million years ago.  This is one of ten species which are the largest placoderms (the class name) to have ever lived, of which Dunkleosteus terrelli was the largest and is most well-known.  The largest collection of Dunkleosteus fossils in the world is housed at the Cleveland Museum of Natural History, but smaller smaller collections are held at the five other museums.  Specimens of Dunkleosteus are on display in many museums throughout the world, most of which are casts of the same specimen, CMNH 5768.  The original CMNH 5768 is on display in the Cleveland Museum of Natural History.

When I looked online, I found Dunkleosteus was named in 1956 to honor David Dunkle, former curator of vertebrate paleontology at the Cleveland Museum of Natural History.  The genus name Dunkleosteus combines Dunkle’s surname with the Greek word ostéon (bone), literally meaning ‘Dunkle’s-bone’.  The type species D. terrelli was first described in 1873 as a species of Dinichthys, its species name was chosen in honor of Jay Terrell, the fossil’s discoverer.  Dunkleosteus could quickly open and close its jaw and had a bite force of 4,414–6,000 N (450–612 kgf; 992–1,349 lbf) at the tip and 5,363–7,400 N (547–755 kgf; 1,206–1,664 lbf) at the blade edge.  Fossils of the various species have been found in North America, Poland, Belgium, and Morocco.  Dunkleosteus was a pelagic (oceanic) fish inhabiting open waters, and an apex predator of its ecosystem. 

One of the problems in estimating size is mainly the armored frontal sections of specimens have been fossilized, and the appearance of the other portions of the fish is mostly unknown.  Only 5% of the fossil Dunkleosteus specimens have more than a quarter of their skeleton preserved.  Reconstructions of the hindquarters are based on fossils of smaller species which have preserved hind sections.  This has caused the size estimates to vary widely.  Various estimations put the length of the largest known specimen between 13 to 33 feet (4.1 to 10 m) long with a weight from 1–4 tons (1.1–4.4 short tons).  A 15 foot (4.6 m) long adult individual has been estimated to have weighed 1,466 pounds (665 kg).   A 2017 study estimated a length of 28.8 feet (8.79 m) based on a regression analysis (statistical modeling), while a 2023 study argued the large sizes were overestimates and proposed a maximum length of 13.5 feet (4.1 m) for the largest known specimen. 

THOUGHTS:  I have found that scientists and theologians both have a hard time saying, “I do not know.”  Science is based on verifiable and reproducible events (facts?), and with the Dunkleosteus there is no evidence for the actual length of the species.  A “best guess” is then couched as an estimate.  Theology is based on the limited human understanding of the divine.  Paul described this as seeing, “through a glass darkly”.  If we already knew everything there would be no need for further scientific research.  If we already understood everything there would be no need for theological study.  We often find ourselves in positions where we do not know, but often choose to give an answer anyway.  Admitting we do not know is not a sign of weakness, it is a show of strength that can open us to other possibilities.  Act for all.  Change is coming and it starts with you.

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