This is Mazon Monday post #16.
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A particularly well-preserved and only partly compressed specimen of Adelophthalmus mazonensis (Meek and Worthen) from the Herdina collection (H-3); × 1.8. The ocellar mound and the short genal spines of the carapace are particularly well preserved.
Found by Eugene Richardson & George Langford; see State of Illinois Scientific Papers Vol. III, No.4, 1948.
Maybe it's their size (early Devonian species could be almost three meters long!) or their similarity to scorpions (they're called sea-scorpions) or their rarity (they are fairly scarce in the fossil record), it's hard to say why, but Eurypterids were fascinating animals. There is currently only one known Mazon Creek species - Adelophthalmus mazonensis. It wasn't very large... maybe a couple inches. But, it is very rare!
George Langford had an entry for Adelophthalmus mazonensis. It can be found here.
Here is the text of the Creature Corner article from September 1988.
Adelophthalmus mazonensis ( eurypterid)
Adelophthalmus mazonensis, previously described under the names of Anthraconectetes mazonensis, Eurypterus mazonensis, Eurypterus (Anthraconecetes) mazonensis and Lepidoderma mazonense, was an eurypterid. It is a member of the Braidwood fauna and of the Mazon Creek Biota.
Eurypterids appear in the fossil record during the Ordovician, reaching their maximum diversity in the Silurian, with some species reaching lengths of 8 to 9 feet. Eurypterid extinction occurred during the Permian, additional victims of the great Permian die-off. During the early Paleozoic, eurypterids were marine animals; by the later Paleozoic they had become inhabitants of the coastal plains, deltas and inshore lagoons adjacent to the seemingly continuous tropical coal swamps. Eurypterids had become the dwellers of brackish to freshwater environments.
Meek and Worthen (1868) described the first eurypterid found in a Mazon Creek concretion, naming it Eurypterus (Anthraconecetes) mazonensis. Yet they made mention of a "very similar" type from Bohemia with the generic name Adelopthalmus. It is always a source of wonder to study Meek and Worthen's original publications. Their works of the last century describe and name fossils that prove to be extremely rare. In many cases ten's of years elapsed before another of the same species was discovered.
Eyrypterids are arthropodous, crustacea-like animals, close relatives of horseshoe crabs, spiders and scorpions. A long rapidly tapering body bears the cephalothorax; a prosoma consisting of a fused head and thorax. The abdomen is ringed by twelve segments, ending in a long tail spine (telson). The prosoma bore two pairs of eyes and six pairs of appendages ("legs") that are progressively longer rearwards. The first pair is the shortest, is chelate (pincer-like) and is located ahead of the mouth (pre-oral), followed by four pairs of walking legs. The last is the longest and is a pair of paddle-like swimming legs. A. mazonensis possessed a small triangular spine on the prosoma, plus spines at the rear of the abdominal segments. Its width was slightly more than 2 inches and its length minus the telson was approximately 6 inches. Complete specimens of Adelophthalmus are extremely rare. Abdominal segments, a prosoma, or an appendage are the "eurypterids" most often found. The body structure denotes an active predator well equipped for a predatorial life in lagoons, marshes and coal swamps. Small fish, amphibians, insects, and perhaps a little cannibalism are assumed for the diet.
In 1966 the late Dr. E. S. Richardson Jr. published "A Tentative Check List of Validly Described Species from the Mazon Creek Faunas". It listed three eurypterids, Adelophthalmus mazonensis, Mazonipterus cyclophthalmus and Mycterops sp. The most recent paper on our subject (now in preparation) takes note that Mycterops sp. Is questionable, being known only from isolated pieces. Author (R. Plotkin) further comments that Richardson, after more research, discarded Mazonipterus c. as a valid species. The described specimen proved to be a leaf scar, a plant fragment; not a prosoma. That leaves our Creature as the eurypterid of the Mazon Creek Biota.
Our Creature is a member of the Phylum: Cheliceriformes; Class Merostomata; Subclass Eurypterida; Genus Adelophthalmus; Species mazonensis.
Found by John M. McLuckie.
Found by George Langford in 1949.
Found by Eugene Richardson & GL; see State of Illinois Scientific Papers Vol. III, No.4, 1948.
