This is Mazon Monday post #136. What's your favorite Mazon Creek fossil? Tell us at email:[email protected]. Thanks!
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Jim Konency wrote this article for the ESCONI newsletter back in May 1997. Jim was president of ESCONI back in the early 1960's. Here's a photo of him at a meeting back in the 1960's. Jim and his wife Sylvia were very active in ESCONI. They eventually retired to Arizona, where he gave students tours of his amazing fossil collection.
The article is interesting. It guesses at an origin and an evolutionary lineage similar to Victoria McCoy's in her excellent presentation at the Mazon Creek Open House.
IS THE TULLY MONSTER REALLY EXTINCT
Jim Konecny
3036 Geronimo Road
Prescott, AZ 86301The subject of extinction is a very complex issue. the answer as to why an organism became extinct is simple Oh, yes, -an organism became extinct because it could not adjust to a changing environment. Now we get to the complexity of the subject. What was the nature of that change? What factor brought about that change?
There are many elements that constitute environmental change; an increase in competition for food; an increase in competition for space; a change in climate - warmer, colder, dryer, wetter; atmospheric change percent of oxygen, CO2, etc.; in the case of - marine organisms, a change in salinity and/or other chemicals; change in water conditions i.e. clarity to name a few. Changes - in any one of these conditions can have a profound effect on the habitat. A habitat can encompass any size area from a small lake or stream to half of a continent. Every creature, every plant on this earth has evolved within a certain complex set of conditions. If these conditions are altered in any way, a species may lose it's ability to exist. However, nature can be kind with it's infinitely variable processes. than others. Some creatures are more adaptable For example, the opossum of North America has been constantly increasing it's range northward whereas there are some fish in Arizona that can exist in only a restricted area of the Colorado River.
To illustrate how complicated this subject can be, let us use the Tully Monster (Tullimonstrum gregarium) as an example. Remains of the Tully Monster have been found only in the middle Pennsylvanian Carbondale Formation, Francis Creek Shale Member of Illinois. They have been found in only three locations near the towns of Morris, Essex and Astoria. Morris and Essex, located in the famous Mazon Creek Area, are about 25 mi. (40km.) apart; Astoria is about 125 mi. (200km.) to the southwest.
The body structure of the Tully Monster is very unique, to say the least (Fig. 1).
Fig.1 Tullimonstrum greqarium - A reconstruction
It was originally referred to as a wormlike fossil and was. described as follows "Abstract: Tullimonstrum gregarium was a common, possibly marine, invertebrate in certain shallow, off shore waters of northern Illinois during the Middle Pennsylvanian. It had a flexible proboscis armed with teeth; a mobile tail; and a curious transverse bar behind the head, bearing a pair of round, external organs." (Richardson, 1966). This unusual body plan has not been found in fossils in younger or older deposits.
Foster (1979b) compares the Tully to modern heteropods, a form of shell-less. planktonic gastropods (Fig. 2). He has specifically made reference to the resemblance to the genus Pterotrachea. In fact, Foster reclassified Tullimonstrum gregarium from indet to Gastropoda.
Fig. 2 Copied from Foster, 1979b. Diagrammatic sketch of Pterotrachea coronata. This specimen is upside down compared to its normal orientation in the water. X 0.8. Abbreviations: (bm) buccal mass; (dt) digestive tract; (e) eye; (p) proboscis; (sf) swimming fin; (t) tail; (vm) visceral mass.
He also made reference to the vague similarity to Opabinia from the lower Cambrian Burgess Shale (Fig.3). Wittington, one of the experts on the Burgess Shale biota, regards Opabinia as belonging to the ancestral stock that gave rise to the arthropods and annelids. It is therefore unlikely that Opabinia regalis is ancestral to Tullimonstrum gregarium. Unless of course, as was originally suggested by Richardson, the Tully actually was an annelid and not a gastropod. However if, as Foster suggests, Tullimonstrum is ancestral to the heteropods, this brings up more questions than answers. Where were these animals between the Pennsylvanian and the present time? No fossils even remotely resembling the Tully have been found in this interim period. Why? Is it because the fossil record is incomplete? This is not likely. since the fauna associated with the Tully, annelids, crustaceans, gastropods, medusae, etc., is found in all ages of rock in this interim period. Even the creatures who, like the Tully Monster, lacked hard parts are found preserved in these sediments.
The spatial limitation of the Tully Monster was a definite disadvantage to it's continued existence. The smaller the habitat area the greater the chances of it's disruption or a destruction.
The Mazon Creek Area is rich in both floral and faunal fossil assemblages, with over 500 plant and animal species having been recorded thus far. Terrestrial, marine, brackish and fresh water biota are represented in this assemblage. The extent of the ocean during Francis Creek time has been well w established (Johnson & Richardson, 1966, 1969; Shabica 1970; Baird, 1979). Location of the shoreline is shown in (Fig. 4). Note that our three locations are situated on this ancient shore.
Fig.4 Approximate extent of the sea. A: Astoria; 0: Ottawa; M: Morris; W: Wilmington; B: Braidwood; E: Essex. After Richardson and Johnson, 1969.
Two seperate assemblages have been established by Johnson and Richardson; the Braidwood Biota which consists of terrestrial and fresh water species and the Essex Biota which consists of marine species. Both contain some of the transitional brackish species. The Mazon Creek. Area has been interpreted as a deltaic environment (Richardson & Johnson, 1969; and Shabica, 1979.) and since the faunal composition at Astoria is similar to that at the Mazon Creek Area we can conclude that the environment was the same. A lower delta plain, delta margin (lagoonal) and delta front are all represented in the sediment complex. The Tully Monster was an inhabitant of the open sea in a near shore environment (Foster, 1979b). Studies have shown that the deposition occurred in a specific uninterrupted sequence similar to present day deltaic action. Floods and storm surges would have had a major effect on the quality and salinity of the water. Since these weather conditions were regular occurrences, the biota must have been able to adjust to these sudden, short term changes. Tropical storms, i.e. hurricanes, though devastating, are not known to have wiped out any animal populations and since there is very little evidence at Mazon Creek of fragmentation of delicate bodies it appears that catastrophic storm conditions were rarely present.
During Pennsylvanian time the North American continent was subjected to at least 50 marine transgressions (Dott & Batten). Several of these transgressions did occupy the area of our subject. No doubt some of these occurred at a slow rate and some at a fast rate, resulting in differential sedimentation rates. Some authors claim that fluctuations of sea level are evident in the depositional sequence. Shabica (1979) states. "Vertical tree trunks preserved in living position are for rapid sedimentation." However, stratigraphic examination of the head wall in the mine near Essex showed no indication that this rapid sedimentation had any effect on the biota. Some cluster patterns of distribution were observed in collecting on the spoil heaps. In as much as this may be an indication of localized communities, this information is of no stratigraphic value. Presently the compiled evidence indicates that the cyclic depositional sequence occurred under normal sea level conditions.
Foster suggested that Tullimonstrum gregarium was an active marine carnivore. The animals that the Tully Monster apparently preyed upon fish, medusae, polychaetes, etc. have withstood - the ravages of extinction. It is therefore unlikely that a loss of food supply was the cause of Tullimonstrum's demise.
There is no evidence of any type of catastrophic event taking place at this time. Whatever caused the Tully Monster's downfall is not apparent in the record written in the rocks. The latest theory on the dinosaurs is that they did not become extinct, but rather that they evolved into birds. Perhaps Foster (1979b) is correct, Tullimonstrum gregarium didn't go extinct, he merely evolved into present day heteropods. Personally I like to think that the Tully Monster appeared on the scene suddenly and just as suddenly disappeared without a trace.
REFERENCES:
Baird, Gordon C. 1979. Lithology and Fossil Distribution, Francis Creek Shale in Northeastern Illinois. In: Mazon Creek Fossils, Matthew H. Nitecki, Ed., Academic Press.Briggs, Derek E.G., Douglass H. Erwin and Frederick J. Collier. 1994. The fossils of the Burgess Shale. Smithsonian Institution.
Carman, Mary R. 1989. The Monster of Illinois. In: Rocks and Minerals, Vol. 64, No. 1, Jan/Feb 1989.
Dott, Robert H., Jr. and Roger L. Batten. 1976. Evolution of the Earth. McGraw-Hill Book Co.
Foster, Merrill W. 1979a. Soft Bodied Coelenterates in the Pennsylvanian of Illinois. In: Mazon Creek Fossils, Matthew H. Nitecki, Ed. Academic Press.
