[D] Santanaraptor placidus [sG] [T]
Describer
Kellner, 1999
Time
Cretaceous Early Albian
Classification
Saurischia Theropoda Tetanurae Coelurosauria ?Maniraptora
Diet
Carnivore
Fossilsite
Santana Formation, [Romualdo Member], Brazil
Length
1.25 meter
Info
Genus - Typespecies
Comments by Mickey Mortimer
Etymology
\\\"Placido\\\'s Santana plunderer\\\", Santana being the formation it was found in and Placido Cidade Nuvens the founder of the Museo de Santana do Cariri. Albian, EC Romualdo member of Santana Formation, Brazil holotype- (MN 4802-V) three caudal vertebrae, chevrons, ischia (91 mm), femora, tibia, fibula, pes, integument, musculature diagnosis- foremon at medial base of lesser trochantor; well developed sulcus on posterior femoral head; fibular trochlea of triangular shape and constricted at base.
Description
This theropod was known first announced in 1996 and emphasis was placed on the soft tissue preserved with the specimen. At that time, it was identified as a probable maniraptoran theropod. It was later described and named in 1999. It was probably about 1.25 meters long, assuming it resembled Ornitholestes in proportions, but was a juvenile according to unfused vertebral sutures. The caudal vertebrae appear to be mid caudals and have low, posteriorly oriented neural spines. The chevrons are said to be half the centrum length and expand slightly anteroposteriorly. The ischia closely resemble Ornitholestes, differing only in the slightly more distally placed obturator process, which is narrower.
Thus, they are of basal coelurosaur grade with a triangular obturator process and unexpanded distal tip. There are no dorsal processes or proximolateral scar and the shaft is rod-shaped distally. The proximal femur is figured, but the distal portion is just described. The shaft diameter is 13 mm and the bone thickness is 2.5 mm, so it\\\'s typically hollow. The wing-like lesser trochantor is separated from the greater trochantor, which it does not reach, by a cleft.
The fourth trochantor is a low crest. The femur has three features unique to this species that are noted above in the diagnosis. The tibia, fibula and pes are photographed (which doesn\\\'t show up well in a photocopy) and not described, although the fibula appears about a third as wide as the tibia. The metatarsus is typically theropod and said to be 70% of the femoral length. Metatarsals II and IV are said to be subequal and it can be seen not to be arctometatarsalian. Digits are also preserved, but no details can be observed.
Soft tissue is found on various parts of the fossil. The epidermis is very thin (~0.04 mm) and formed by irregular quadrangles separated by deep grooves. There are no scales or feathers preserved. Striated muscle fibers were preserved as calcium phosphate, are polygonal in transverse section and 30-50 micrometers in diameter.
The bone still preserves channels for blood vessels (diameter 20-25 micrometers) and lacunae for osteocytes (diameter ~5 micrometers). There are also structures preserved that may either be mineralizations filling the bone\\\'s capillaries or replacements of the blood vessels. They are rod-like with a rough outer layer and smooth inner layer. Relationships- Kellner places this species in the Coelurosauria based on the triangular obturator process and suggests it may be a Maniraptoriform based on Sereno\\\'s (1999) character \\\"obturator notch U-shaped with slightly divergent sides\\\", which I find highly variable. I agree that the triangular obturator process shows this is a coelurosaur, but the wing-like lesser trochantor excludes it from the Maniraptora (oviraptorosaurs, [segnosaurs], dromaeosaurs, troodontids, alvarezsaurs, birds and a few more taxa in my analysis, a wing-like lesser trochantor is only known in Beipiaosaurus).
The lack of a proximolateral ischial scar excludes it from the Tyrannosauroidea. That leaves it in the large group of basal coelurosaurs/maniraptoriforms including compsognathids, Coelurus, Ornitholestes, Scipionyx, Nedcolbertia, Nqwebasaurus, Gasosaurus, ornithomimosaurs and the new Santana coelurosaur (Martill et al. 2000). These groups also all have plesiomorphically low lesser trochantors and prominent fourth trochantors where known.
These are currently in an unresolved polytomy with tyrannosaurs and maniraptorans in my analysis, so all coelurosaurs except for Deltadromeus are in a messy Maniraptoriformes. Whether Santanaraptor will actually be in the most inclusive group with ornithomimosaurs and maniraptorans when my cladogram clears up remains to be seen, so I recommend Santanaraptor be placed as a non-maniraptoran, non-tyrannosaurian coelurosaur.
It may be noted however that of the basal coelurosaurs listed above, only Santanaraptor and Ornitholestes lack distal ischial expansions, so perhaps they are more derived (though my analysis has yet to show this).
References
Kellner, A. W. A. 1996. Fossilized theropod soft-tissue. Nature 379: 32.
Kellner, A.W.A. and D.A. Campos. 1998. Archosaur soft Tissue from the Cretaceous of the Araripe Basin, Northeastern Brazil. Boletim do Museu
Nacional, Geologia No. 42: 1-22.
Kellner, A.W.A. 1999. Short note on a new dinosaur (Theropoda, Coelurosauria) from the Santana Formation (Romualdo Member, Albian),
Northeastern brazil. Boletim do Museu Nacional (Rio de Janeiro, Brasil), N.S. No. 49: 8 p.
Other comments
Santanaraptor placidus is based mostly on bones from the rear end and suggests it may be an maniraptoriform coelurosaur. It has a big obturator notch and a few other apomorphies. Santanaraptor is housed in the Museu Nacional, Universidade Federal do Riode Janeiro. The specimen number is MN 4802-V. This is the same specimenwith soft tissue preservation previously mentioned by Kellner in his 1996 paper in Nature (379:32). \\\"Santanaraptor is much smaller than the Santana \\\'oviraptorosaur\\\': however, because the specimens do not overlap in terms of material, it cannot beresolved if they are the same taxon. Futhermore, Kellner reports that additional specimens of theropods larger than Santanaraptor are known and awaiting description.
Kellner, 1999
Time
Cretaceous Early Albian
Classification
Saurischia Theropoda Tetanurae Coelurosauria ?Maniraptora
Diet
Carnivore
Fossilsite
Santana Formation, [Romualdo Member], Brazil
Length
1.25 meter
Info
Genus - Typespecies
Comments by Mickey Mortimer
Etymology
\\\"Placido\\\'s Santana plunderer\\\", Santana being the formation it was found in and Placido Cidade Nuvens the founder of the Museo de Santana do Cariri. Albian, EC Romualdo member of Santana Formation, Brazil holotype- (MN 4802-V) three caudal vertebrae, chevrons, ischia (91 mm), femora, tibia, fibula, pes, integument, musculature diagnosis- foremon at medial base of lesser trochantor; well developed sulcus on posterior femoral head; fibular trochlea of triangular shape and constricted at base.
Description
This theropod was known first announced in 1996 and emphasis was placed on the soft tissue preserved with the specimen. At that time, it was identified as a probable maniraptoran theropod. It was later described and named in 1999. It was probably about 1.25 meters long, assuming it resembled Ornitholestes in proportions, but was a juvenile according to unfused vertebral sutures. The caudal vertebrae appear to be mid caudals and have low, posteriorly oriented neural spines. The chevrons are said to be half the centrum length and expand slightly anteroposteriorly. The ischia closely resemble Ornitholestes, differing only in the slightly more distally placed obturator process, which is narrower.
Thus, they are of basal coelurosaur grade with a triangular obturator process and unexpanded distal tip. There are no dorsal processes or proximolateral scar and the shaft is rod-shaped distally. The proximal femur is figured, but the distal portion is just described. The shaft diameter is 13 mm and the bone thickness is 2.5 mm, so it\\\'s typically hollow. The wing-like lesser trochantor is separated from the greater trochantor, which it does not reach, by a cleft.
The fourth trochantor is a low crest. The femur has three features unique to this species that are noted above in the diagnosis. The tibia, fibula and pes are photographed (which doesn\\\'t show up well in a photocopy) and not described, although the fibula appears about a third as wide as the tibia. The metatarsus is typically theropod and said to be 70% of the femoral length. Metatarsals II and IV are said to be subequal and it can be seen not to be arctometatarsalian. Digits are also preserved, but no details can be observed.
Soft tissue is found on various parts of the fossil. The epidermis is very thin (~0.04 mm) and formed by irregular quadrangles separated by deep grooves. There are no scales or feathers preserved. Striated muscle fibers were preserved as calcium phosphate, are polygonal in transverse section and 30-50 micrometers in diameter.
The bone still preserves channels for blood vessels (diameter 20-25 micrometers) and lacunae for osteocytes (diameter ~5 micrometers). There are also structures preserved that may either be mineralizations filling the bone\\\'s capillaries or replacements of the blood vessels. They are rod-like with a rough outer layer and smooth inner layer. Relationships- Kellner places this species in the Coelurosauria based on the triangular obturator process and suggests it may be a Maniraptoriform based on Sereno\\\'s (1999) character \\\"obturator notch U-shaped with slightly divergent sides\\\", which I find highly variable. I agree that the triangular obturator process shows this is a coelurosaur, but the wing-like lesser trochantor excludes it from the Maniraptora (oviraptorosaurs, [segnosaurs], dromaeosaurs, troodontids, alvarezsaurs, birds and a few more taxa in my analysis, a wing-like lesser trochantor is only known in Beipiaosaurus).
The lack of a proximolateral ischial scar excludes it from the Tyrannosauroidea. That leaves it in the large group of basal coelurosaurs/maniraptoriforms including compsognathids, Coelurus, Ornitholestes, Scipionyx, Nedcolbertia, Nqwebasaurus, Gasosaurus, ornithomimosaurs and the new Santana coelurosaur (Martill et al. 2000). These groups also all have plesiomorphically low lesser trochantors and prominent fourth trochantors where known.
These are currently in an unresolved polytomy with tyrannosaurs and maniraptorans in my analysis, so all coelurosaurs except for Deltadromeus are in a messy Maniraptoriformes. Whether Santanaraptor will actually be in the most inclusive group with ornithomimosaurs and maniraptorans when my cladogram clears up remains to be seen, so I recommend Santanaraptor be placed as a non-maniraptoran, non-tyrannosaurian coelurosaur.
It may be noted however that of the basal coelurosaurs listed above, only Santanaraptor and Ornitholestes lack distal ischial expansions, so perhaps they are more derived (though my analysis has yet to show this).
References
Kellner, A. W. A. 1996. Fossilized theropod soft-tissue. Nature 379: 32.
Kellner, A.W.A. and D.A. Campos. 1998. Archosaur soft Tissue from the Cretaceous of the Araripe Basin, Northeastern Brazil. Boletim do Museu
Nacional, Geologia No. 42: 1-22.
Kellner, A.W.A. 1999. Short note on a new dinosaur (Theropoda, Coelurosauria) from the Santana Formation (Romualdo Member, Albian),
Northeastern brazil. Boletim do Museu Nacional (Rio de Janeiro, Brasil), N.S. No. 49: 8 p.
Other comments
Santanaraptor placidus is based mostly on bones from the rear end and suggests it may be an maniraptoriform coelurosaur. It has a big obturator notch and a few other apomorphies. Santanaraptor is housed in the Museu Nacional, Universidade Federal do Riode Janeiro. The specimen number is MN 4802-V. This is the same specimenwith soft tissue preservation previously mentioned by Kellner in his 1996 paper in Nature (379:32). \\\"Santanaraptor is much smaller than the Santana \\\'oviraptorosaur\\\': however, because the specimens do not overlap in terms of material, it cannot beresolved if they are the same taxon. Futhermore, Kellner reports that additional specimens of theropods larger than Santanaraptor are known and awaiting description.