"Syntarsus" "mexicanum"

Thanks to Pixagono, Harris, Chure and Scheetz for their combined work in finding this new theropod name.  It turns out the proper reference is-

Hernandez, 2002. Los dinosaurios en Mexico. in Gonzalez Gonzalez and De Stefano Farias (eds.). Fosiles de Mexico: Coahuila, una Ventana a Traves del Tiempo. Gobierno del Estado de Coahuila, Saltillo. 143-153.

Unfortunately, the entire section mentioning the species is-

"Otro material del grupo de los dinosaurios saurisquios (Cintura tipo reptil) ha sido determinada como una nueva especie del genero Syntarsus, llamada familia Syntarsus mexicanum, de la familia Coelophysidae: se trata de pequenos dinosaurios carnivoros de cuerpo esbelto y de 3 metros de longitud en promedia."

Or translated-

"Other material of the saurischian dinosaur group (reptile pelvic type) has been determined as a new species of the genus Syntarsus, named Syntarsus mexicanum family[sic?], of the family Coelophysidae: they are small carnivorous dinosaurs with a slender body and are 3 meters long on average."


Thus it is a nomen nudum for not including a diagnosis (ICZN 13.1.1) (the slender body and 3 meter length seem to refer to the family, not the species) or a type specimen (ICZN 16.4.1).  Harris wondered if Hernandez had planned to have an official description out by the time the book was published, but given the explicit designation of this as a new species, I don't see any evidence for that.  To the contrary, I'm curious if the apparent typo "llamada familia" used in reference to the species doesn't mean "familiar name", as in "informal name", and Hernandez didn't intend to name a new species at all.  In any case, I stand by my previous conclusion "S." "mexicanum" probably refers to the coelophysid material described by Munter and Clark (2006).  This is because the latter material comes from the locality Hernandez mentions "mexicanum" as being from ("Esta localidad descubierta en 1982 por el doctor James M. Clark") and was found to be sister to Megapnosaurus (as Syntarsus) by Munter (1999- SVP abstract and thesis).  In fact, it probably refers to the dorsals, sacrum and pelvis IGM 6624 specifically, since Hernandez also states "tambien se han identificado elementos craneales del genero Ceratosaurus", and the cranial specimen IGM 6625 was thought by Munter to be either a neoceratosaur or maniraptoran.

Probable intended holotype of "Syntarsus" "mexicanum", vertebrae and pelvis IGM 6624 in lateral view after Munter and Clark, 2006).

The Database's entry will be-

"Syntarsus" "mexicanum" Hernandez, 2002
Toarcian, Early Jurassic
La Boca Formation, Mexico
Material- (IGM 6624) partial twelfth dorsal vertebra (13.1 mm), partial thirteenth dorsal vertebra (20 mm), partial synsacrum (61.5 mm- 16.2, 12.7, 9.6, 9.6, 13.4 mm), incomplete fused pelvis
?...(IGM 6625) posterior braincase, incomplete laterosphenoid, fragments
Diagnosis- (after Munter, 1999) ilia contact dorsally on midline (may be taphonomic).
Comments- Discovered in 1994, Munter (1999) found IGM 6624 to be sister to Megapnosaurus (as Syntarsus) based on the antitrochanter projecting into the acetabulum (though this is also present in Coelophysis and Liliensternus). It differs in having ilia contact sacral neural spines two and three. The skull fragments may not belong to the same individual or taxon and were thought to be a neoceratosair or maniraptoran by Munter due to their pneumatized paroccipital roots. However, this has since been found to exist in coelophysids such as "M." kayentakatae, making the possibility it belongs to the same individual more likely. Hernandez (2002) erected a new species Syntarsus mexicanum from the locality, which is probably based on IGM 6624 since no other coelophysoid specimens have been reported from there and Munter emphasized similarity to what he called Syntarsus. However, it is a nomen nudum for not including a diagnosis (ICZN 13.1.1) or a type specimen (ICZN 16.4.1). Hernandez also mentioned cranial elements of Ceratosaurus, which are probably IGM 6625 based on Munter's comparison to neoceratosaurs. Munter and Clark later (2006) described the specimens and included IGM 6624 in Carrano et al.'s (2002) matrix where it emerged sister to Coelophysis+Megapnosaurus (excluded due to lacking fused sacral neural spines), and Rauhut's (2003) matrix where it was in the clade of Coelophysis+Megapnosaurus (the latter a chimaera of rhodesiensis and kayentakatae). They considered IGM 6625 provisionally theropod. The only potential apomorphy noted in the material has been the ilia which meet at the midline, but this may be taphonomic. Munter and Clark note that the dorsally oriented acetabulum suggests distortion, but the rugose medial ilial surface suggesting contact with the other ilium and general lack of distortion in other fossils from the locality suggests it was natural. As "mexicanum" has not been shown to be closer to Megapnosaurus than to Coelophysis, it is here retained under the name "Syntarsus" "mexicanum".
References- Clark, Montellano, Hopson, Hernandez and Reynoso, 1998. The Jurassic vertebrates of Huizachal canyon, Tamaulipas. Avances en Investigacion, Paleontologia de Vertebrados. Universidad Autonoma del Estado de Hidalgo Publicacion Especial 1. 1-3.
Munter, 1999. Two theropod dinosaur specimens from Huizachal Canyon, Mexico. Journal of Vertebrate Paleontology. 19(3), 65A.
Munter, 1999. Two theropod dinosaur specimens from Huizachal Canyon, Mexico. Masters thesis. George Washington University.
Hernandez, 2002. Los dinosaurios en Mexico. in Gonzalez Gonzalez and De Stefano Farias (eds.). Fosiles de Mexico: Coahuila, una Ventana a Traves del Tiempo. Gobierno del Estado de Coahuila, Saltillo. 143-153.
Munter and Clark, 2006. Theropod dinosaurs from the Early Jurassic of Huizachal Canyon, Mexico. In Carrano, Gaudin, Blob, Wible (eds.). Amniote paleobiology: Perspectives on the evolution of mammals, birds, and reptiles. University of Chicago Press, Chicago. 53-75.