Przeglqd Geologiczny, vol. 43, nr 2, 1995

o tyreoforowym pochodzeniu slad6w Otozoum

Gerard Gierlinski*

Otozoum to jeden z najbardziej kontrowersyjnych ich­ slad6w innych zwierzqt, kt6rym wspomniane slady dIoni notakson6w w dziejach paleoichnologii. lednoczeSnie byl mozna by bylo przypisac. Ponadto w oparciu 0 rekonstru­ jednym z najwczesniej opisanych slad6w krt

Thyreophoran affinity of Otozoum tracks

Gerard Gierlinski*

Otozoum is one of the most controversial tetrapod ich­ A.C.SI14), have not been left by the same creature. How­ notaxon. It was one of the first trace discovered and ever, there are no ichnites of anothertrackmaker, whose such described from the Liassic deposits of Newark Supergroup, manus impressions could be. Manus imprints are too large in eastern North America [7]. Debate on its affinity has not (20 cm long) to be produced by the anomoepodid trackma­ been over since past century, still being one of the most kef. In my opinion both ichnites of pes and manus alike, were intriguing ichnological dilemma. left by the same trackmaker. The trackmaker was simply Lull in his final revision of Hitchcock' s classification resting or feeding a moment quadrupedally and after that it considered Otozoum as the prosauropod track [11]. Later, came back to bipedal walking posture overprinting its front Olsen and Galton [12] noted that Otozoum manus impres­ track by hind one (Fig. 1). For that reason manus impressions sion indicates an osteological structure wholly unlike that are heavier imprinted than the pes ones, which were left of any known prosauropod. In opinions of Schmidt [16], during the "regular" walking gait. Firstly, trackmaker arms Baird [1] , Haubold [S , 6], Olsen and Galton [12], Olsen took almost whole load of the forward replacement of gra­ and Padian [13], Otozoum ichnites are more likely to be vity center, when came down on four rapidly. Se­ the tracks of others than , they are tracks condly, arms were used to help the animal to rise from a of thecodontians or crocodilians. However, I agree with prone position. Lockley who argued that Otozoum trackmaker belonged Thulborn [18] regarded Otozoum as ornithischian track. to dinosaurs [8, 9]. On the other hand, previous authors He assigned it to the ornithopod footprints. Considering the are also right that Otozoum manus does not fit the prosau­ ornithischian - like fashioned manus of Otozoum, Thul­ ropod manus. born's identifications seems to be the most sensible, but Farlow [3] concluded that the manus impressions which ornithopod affinity of Otozoum is rather inconceivable to ass ociate with the Otozoum pes imprints (in specimen me. Functionally tetradactyl pes of Otozoum trackmaker is unusual for ornithopods. Among early ornithischians the * Panstwowy Instytut Geologiczny, ul. Rakowiecka 4, best candidate to be a Otozoum trackmaker is Scelidosaurus. 00-975 Warszawa The osteological reconstruction of the Otozoum trackmaker

123 Przeglqd Geologicmy, vol. 43, nr 2, 1995

pes bears a resemblance to the Scelidosaurus harrisonii foot hallux more developed. Moreover, O. modii tracks reach the skeleton (Fig. 2). length of 49 cm, whereas, the S. harrisonii foot is 27 cm long. However, the Otozoum moodii trackmaker was more In the Glen Canyon Group of western North America, Oto­ advanced phylogenetically or ontogenetically than Sce lido­ zoum occurs in the Late Liassic (Pliensbachian - Toarcian) saurus harrisonii was. The osteological reconstruction of. strata of Navajo Formation [8], while English Scelidosaurus O. moodii (A.CAIl) differs from S. harrisonii pes by having remains are Early Liassic (Sinemurian) in age. Mentioned

Fig. 1. Gait restoration of an Otowum trackmaker, based on the trackway A.C.S/14, from the Early of Massachusetts, USA

Rye. 1. Rekonstrukcja ruchu zwierz~cia na podstawie szlaku trop6w Otozown (A.C.S/14), z wczesnej jury Massachusetts, USA

IV

~. 'f f:~~:~~

~ ~ . ~.,~. ", . '"1-.'~i''~''' ...:.; ...... ,.~:. ". ," ~I '.~.;.4"(..... ,)1

A .C.4/1 Scelidosaurus harrisonii pes after Owen 1863

Fig. 2. The osteological reconstruction of Otowwn moodii (A.eA/I), from the Early Jurassic of Massachusetts, USA, in comparison with the foot of Scelidosaurus harrisonii from the Early Jurassic of England Rye. 2. Rekonstrukcja osteologiczna Otowwn moodii (A.C.4/ I) z wczesnej jury Massachusetts, USA, w zestawieniu ze szkieletem stopy Sce/idosaurus harrisonii z wczesnej jury AngIii

124 Przeglqd Geologiczny, vol. 43, Ilr 2, 1995

Fig. 3. Phylogenetic relationships of DraW L/m to ot­ her tracks and their possible thyreophoran trackma­ kers 'pes

Rye. 3. Pokrewieristwo filogenetyczne DraW L/m z innymi tropami i przypisywanymi im stopami tyreo­ forow

longed to different taxon from S. harrisonii, both were closely related having the transitional pes morphology between the primitive thyreopho­ rans (Scutellosaurus) and ankylosaurs (Fig. 3). Nodosaurus pes, after Lull 1921 Abbreviation of cited repositories: A.e.­ Te/rapodosaurus, after Sternberg 1932 Pratt Museum of Natural History, Arnherst Col­ lege, Amherst, Massachusetts, USA; U.e. - Field Museum of Natural History, Chicago, Illi­ nois, USA.

References

BAIRD D. 1980 - [In:] Jacobs L.L (ed.), Aspects of Vertebrate History. Museum of North­ ern Arizona Press, Flagstaff: 219-230.

~§. I 2 COLBERT E.H. 1981 - Bull. Mus. North. Ari­ zona, 53: 1-61. Scelidosaurus pes, after 3 FARLOW J.O. 1992 - Zubia, 10: 89-138. OweD 1863 O/ozoum, A.C. 411 4 GRANTHAM R.G. 1989 - [In:] Gillette D.D., Lock1ey M.G. (eds.), Tracks and Tra­ ces. Cambridge University Press, Cambridge: 281-284. 5 HAUBOLD H. 1984 - Saurierfahrten. A. Ziem­ sen Verlag, Wittenberg Lutherstadt. 6 HAUBOLD H. 1986 - [In:] Padian K (ed.), The Beginning of the Age of Dinosaurs: Faunal change across the -Jurassic boundary. Cambridge University Press, Cambridge: 189- 3· ~ 201. 7 HITCHCOCKE. 1847 - Amer. Jour. Sci., (2) 4: 46-57. I 8 LOCKLEY M.G. 1990 - Canyon Legacy, A Scutellosaurus pes, Anomoepus. U.c. 457 Journal of the Dan O'Laurie Museum, Moab, 6: after Colbert 1981 2-8. 9 LOCKLEY M.G. 1991-Tracking Dinosaurs: data suggests that Otozoum was left by phylogenetically A New Look at an Ancient World. Cambridge University Press, Cambridge. more advanced thyreophoran member than Scelidosaurus 10 LULL R.S. 1921 - Amer. Jour. Sci., (5) 1: 97-126. was. However, another facts support different conclusion. 11 LULL R.S. 1953 - State Geol. Nat. Hist. Survey of Con­ Padian [15] described Scelidosaurus dermal scutes from necticut, Bull., 81: 1-336. the Kayenta Formation (Sinemurian - Pliensbachian) of 12 OLSEN P.E. , GALTON P.M. 1984 - Palaeontoiogia Afri­ northern Arizona. On the other side, in the Newark Supergroup, cana (Haughton Memorial Volume), 25 : 87-110. Otozoum was discovered in the Early Liassic (Hettangian) 13 OLSEN P.E., PADIAN K 1986 - [In:] Padian K (ed.), deposits of Nova Scotia [4]. Among the Connecticut Valley The Beginning of the Age of Dinosaurs: Faunal change ac­ tracks, one Otozoum specimen shows shorter hallux than others ross the Triassic-Jurassic boundary. Cambridge University do, which corresponds to the S. harrisonii hallux length. As Press, Cambridge: 259- 273. Lull [11] noted first digit of this footprint is reaching only to 14 OWEN R. 1863 - Palaeont. Soc. Monograph., 14: 1- 28. 15 PADIANK1989-Geology, 17:438--441. the base of the second one. Such exeption in the Otozoum 16 SCHMIDT H. 1959 - Abh. Hess. Landesant Boden­ morphology makes possible to conclude that the hallux forsch. , 28 : 1-137. length might be determined by the intraspecific variation. 17 STERNBERG CM. 1932 - Annual Report of the Natio­ Juveniles could have less developed hallux than adults. nal Museum of Canada, 1930: 59- 85. Scelidosaurus harrisonii might represents then less matured 18 THULBORN T. 1990 - Dinosaur Tracks. Chapman and individual. Consequently, even if Otozoum trackmaker be- Hall, London.

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