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Re: Apatosaurus alenquerensis
In a message dated 98-07-30 20:30:56 EDT, firstname.lastname@example.org writes:
<< So it seems an appropriate time to ask about the status of Apatosaurus
alenquerensis de Lapparent & Zbyszewski 1957 (Kimmeridgian, Portugal).
Judging from published illustrations, it surely isn't Apatosaurus. In 1990
("The Dinosauria") MacIntosh suggested its affinities lay with Camarasaurus
- which (with all deference to his far superior knowledge) strikes me as
equally unconvincing. More recently Wilson & Sereno (1998 SVP Memoirs)
raised a third possibility - which escapes me, as I'm working from memory. >>
Several years ago, when I was researching for a certain popular dinosaur
encyclopedia whose title I won't mention here, I wrote the following for the
Etymology: alenquerensis, Latin for "from Alenquer," the Portugese town near
where the type skeleton was discovered
Average adult size: At least 65 feet (20 m) long
Average adult weight: At least 15-20 tons (15,000-20,000 kg)
Range: Southern Europe (Portugal)
Period: Late Jurassic ("Lusitanian" or Oxfordian to Kimmeridgian stages, about
152-157 million years ago)
Camarasaurus alenquerensis is one of the largest known camarasaurids.
skeleton discovered in Portugal were more complete, it would be about as large
as the Apatosaurus louisae mounted at the Carnegie Museum of Natural History,
and it would actually stand somewhat taller, because the front legs were about
two feet (60 cm) longer than those of A. louisae. The pelvis was over 4 feet
(125 cm) long, and the thigh bones were almost 6 feet (174 cm) long. Because
the neural arches of the vertebrae are missing, it is quite possible that the
skeleton belonged to an immature animal, in which the arches had not yet grown
firmly attached to the vertebrae. So a fully adult C. alenquerensis could well
have been even larger.
Correctly classifying this species has proved puzzling to
have studied the skeleton. It is so large that the original describers thought
it was an Apatosaurus, and because the shapes of key bones such as the
shoulder blades and pelvic bones were different from those of Apatosaurus ajax
and Apatosaurus louisae, they gave it the new name Apatosaurus alenquerensis.
Some paleontologists later thought that the long front legs made it a
brachiosaurid, but in 1990 John S. McIntosh showed that it was a camarasaurid.
He thought it was possible that it represented a new genus, but because the
skeleton was so incomplete, he tentatively placed the species into the already
established genus Camarasaurus rather than create a brand-new name for it.
Assuming that this species belongs to the genus Camarasaurus, it
the well-known American species of Camarasaurus mainly in having had
relatively longer forelimbs. Otherwise, we can guess that its head was
probably short and boxlike, and that it had the spoon-shaped teeth typical of
camarasaurids. One such fossil tooth, from Ourem, a town about 40 miles (60
km) north of Alenquer, was referred to the obsolete camarasaurid species
Morosaurus marchei by Henri-Émile Sauvage in 1897. It is of the right size and
shape to have once been in the jaw of a Camarasaurus alenquerensis.
Discoverer: Harold Weston Robbins (an American geologist employed by the
Portuguese Petroleum Company)
When discovered: Sometime prior to June, 1949
Where discovered: In gray and pink clays of an unnamed formation near the
ruins of Moinho do Carmo mill, about 1.5 km south of Alenquer, Estremadura
Describers: Albert F. de Lapparent and Georges Zbyszewski
Year described: 1957
Type specimen: An incomplete skeleton including 4 cervical, 11 dorsal, and 11
caudal vertebrae, all lacking neural arches; pectoral and left forelimb
elements, pelvic and left hindlimb elements, and ribs; this material
(unnumbered) is currently kept at the Portuguese Geological Service Museum,
Other important specimens: 15 or 16 caudal vertebrae from San Bernardino
Beach, Beira Littoral Province, Portugal, discovered by H. da Costa Cabaço in
February, 1946; several other large sauropod bones from various localities in
Portugal referred to this species by the describers; a camarasaurid tooth from
Ourem originally referred to Morosaurus marchei and referred to this species
by the describers
Current status: Valid species; originally described as Apatosaurus
alenquerensis, but shown in 1987 to be a camarasaurid sauropod by Michael A.
Raath and John S. McIntosh, who tentatively referred the species to the genus
Camarasaurus; also called Atlantosaurus alenquerensis by Rodney Steel in 1970
and Brontosaurus alenquerensis by George Olshevsky in 1978; further research
may indicate that this species belongs to a new genus.
As a footnote to this, Wilson & Sereno note (p. 20) that McIntosh probably
referred this species to _Camarasaurus_ correctly, based on the known
material, and that the known material doesn't warrant a new genus just yet.