Re-evaluating “Apatosaurus” minimus,
a bizarre Morrison Formation sauropod
with diplodocoid and macronarian features
Michael P. Taylor and Mathew J. Wedel
Department of Earth Sciences
University of Bristol
England
College of Osteopathic Medicine of the Pacific
and College of Podiatric Medicine
Western University of Health Sciences
California, USA.
The Morrison Formation
1.5 million km2; 9.5 million years (156.3±2 Mya to 146.8±1 Mya)
Many sauropod genera in the Morrison
Valid
Apatosaurus
Barosaurus
Brachiosaurus
Camarasaurus
Diplodocus
Haplocanthosaurus
Supersaurus
Suuwassea
Apatosaurus ajax holotype YPM 1860
Cervical vertebra, left lateral view
Many sauropod genera in the Morrison
Valid
Apatosaurus
Barosaurus
Brachiosaurus
Camarasaurus
Diplodocus
Haplocanthosaurus
Supersaurus
Suuwassea
Questionable
Amphicoelias
Dyslocosaurus
[if Jurassic)]
Dystrophaeus
Eobrontosaurus
Amphicoelias fragillimus holotype AMNH 5777
Dorsal vertebral neural arch, posterior view
Many sauropod genera in the Morrison
Valid
Apatosaurus
Barosaurus
Brachiosaurus
Camarasaurus
Diplodocus
Haplocanthosaurus
Supersaurus
Suuwassea
Questionable
Amphicoelias
Dyslocosaurus
[if Jurassic)]
Dystrophaeus
Eobrontosaurus
Dystylosaurus edwini holotype BYU 4503
Dorsal vertebral, right anterolateral view
Synonymised
Atlantosaurus
Brontosaurus
Cathetosaurus
Dystylosaurus
Elosaurus
Morosaurus
Seismosaurus
Uintasaurus
Ultrasauros [sic]
Many sauropod genera in the Morrison
Valid
Apatosaurus
Barosaurus
Brachiosaurus
Camarasaurus
Diplodocus
Haplocanthosaurus
Supersaurus
Suuwassea
Questionable
Amphicoelias
Dyslocosaurus
[if Jurassic)]
Dystrophaeus
Eobrontosaurus
Synonymised
Atlantosaurus
Brontosaurus
Cathetosaurus
Dystylosaurus
Elosaurus
Morosaurus
Seismosaurus
Uintasaurus
Ultrasauros [sic]
Many sauropod genera in the Morrison
Valid
Apatosaurus
Barosaurus
Brachiosaurus
Camarasaurus
Diplodocus
Haplocanthosaurus
Supersaurus
Suuwassea
Questionable
Amphicoelias
Dyslocosaurus
[if Jurassic)]
Dystrophaeus
Eobrontosaurus
Not yet named
New diplodocoid (Vietti and Hartman 2004)
AMNH diplodocine
"Apatosaurus" minimus
Synonymised
Atlantosaurus
Brontosaurus
Cathetosaurus
Dystylosaurus
Elosaurus
Morosaurus
Seismosaurus
Uintasaurus
Ultrasauros [sic]
Apatosaurus
Composite skeleton on display
in public gallery at AMNH.
Apatosaurus has many species
Apatosaurus ajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus,
grandis, laticollis, amplus, alanquerensis
Apatosaurus (= “Brontosaurus”) excelsus holotype YPM 1980
Apatosaurus has many species
Apatosaurus ajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus,
grandis, laticollis, amplus, alanquerensis
Apatosaurus (= “Brontosaurus”) excelsus holotype YPM 1980
Apatosaurus has many species
Brontosaurus
Elosaurus
Apatosaurus ajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus,
grandis, laticollis, amplus, alanquerensis
Atlantosaurus montanus, immanis
Apatosaurus (= “Brontosaurus”) excelsus holotype YPM 1980
Apatosaurus has many species
Brontosaurus
Elosaurus
Apatosaurus ajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus,
grandis, laticollis, amplus, alanquerensis
Camarasaurus grandis
Atlantosaurus montanus, immanis
Lourinhasaurus
Eobrontosaurus
???
Apatosaurus (= “Brontosaurus”) excelsus holotype YPM 1980
Apatosaurus species
Upchurch et al. (2005)
Figure 15.
Specimen-level
phylogenetic analysis
Strict consensus
What is AMNH 675?
Henry Fairfield Osborn (1904)
Figure 4.
“Anterior, posterior and left
lateral views of the sacrum and
ilium of Brontosaurus sp.
No. 675, Amer. Mus.”
“The inferior view of these
vertebrae corresponds in
character with Marsh's figures
of Brontosaurus excelsus and
of B. amplus.”
What is AMNH 675?
Charles C. Mook (1917)
Figure 2.
“A. Outline of right pubis
of Apatosaurus minimus.
B. Outline of right ischium
of Apatosaurus minimus.”
No reason given for
association of material.
Why is AMNH 675 Apatosaurus?
“It appears that the well-preserved sacrum and pelvis
of No. 675 of the American Museum collections belongs
to a species of Apatosaurus which has not hitherto
been described.”
Why is AMNH 675 Apatosaurus?
“It appears that the well-preserved sacrum and pelvis
of No. 675 of the American Museum collections belongs
to a species of Apatosaurus which has not hitherto
been described.”
“The inferior portion of the sacral rib of primary sacral 2
has an oblique ridge on its inferior surface resembling
those present in the types of A. ajax, Brontosaurus
excelsus, and B. amplus. This is a characteristic structure
in Apatosaurus. The inferior surfaces of the centra are
broadly rounded, contrasting with those of Diplodocus. The
inferior portions of the sacral ribs are not twisted as in
Camarasaurus. These characters together with the tall
spines which have the characteristic Apatosaurus lamination
indicate conclusively that the specimen under consideration
belongs to the genus Apatosaurus.”
Why is AMNH 675 Apatosaurus?
“It appears that the well-preserved sacrum and pelvis
of No. 675 of the American Museum collections belongs
to a species of Apatosaurus which has not hitherto
been described.”
“The inferior portion of the sacral rib of primary sacral 2
has an oblique ridge on its inferior surface resembling
those present in the types of A. ajax, Brontosaurus
excelsus, and B. amplus. This is a characteristic structure
in Apatosaurus. The inferior surfaces of the centra are
broadly rounded, contrasting with those of Diplodocus. The
inferior portions of the sacral ribs are not twisted as in
Camarasaurus. These characters together with the tall
spines which have the characteristic Apatosaurus lamination
indicate conclusively that the specimen under consideration
belongs to the genus Apatosaurus.”
Why is AMNH 675 Apatosaurus?
“It appears that the well-preserved sacrum and pelvis
of No. 675 of the American Museum collections belongs
to a species of Apatosaurus which has not hitherto
been described.”
“The inferior portion of the sacral rib of primary sacral 2
has an oblique ridge on its inferior surface resembling
those present in the types of A. ajax, Brontosaurus
excelsus, and B. amplus. This is a characteristic structure
in Apatosaurus. The inferior surfaces of the centra are
broadly rounded, contrasting with those of Diplodocus. The
inferior portions of the sacral ribs are not twisted as in
Camarasaurus. These characters together with the tall
spines which have the characteristic Apatosaurus lamination
indicate conclusively that the specimen under consideration
belongs to the genus Apatosaurus.”
Why is AMNH 675 Apatosaurus?
“It appears that the well-preserved sacrum and pelvis
of No. 675 of the American Museum collections belongs
to a species of Apatosaurus which has not hitherto
been described.”
“The inferior portion of the sacral rib of primary sacral 2
has an oblique ridge on its inferior surface resembling
those present in the types of A. ajax, Brontosaurus
excelsus, and B. amplus. This is a characteristic structure
in Apatosaurus. The inferior surfaces of the centra are
broadly rounded, contrasting with those of Diplodocus. The
inferior portions of the sacral ribs are not twisted as in
Camarasaurus. These characters together with the tall
spines which have the characteristic Apatosaurus lamination
indicate conclusively that the specimen under consideration
belongs to the genus Apatosaurus.”
Why is AMNH 675 Apatosaurus?
“It appears that the well-preserved sacrum and pelvis
of No. 675 of the American Museum collections belongs
to a species of Apatosaurus which has not hitherto
been described.”
“The inferior portion of the sacral rib of primary sacral 2
has an oblique ridge on its inferior surface resembling
those present in the types of A. ajax, Brontosaurus
excelsus, and B. amplus. This is a characteristic structure
in Apatosaurus. The inferior surfaces of the centra are
broadly rounded, contrasting with those of Diplodocus. The
inferior portions of the sacral ribs are not twisted as in
Camarasaurus. These characters together with the tall
spines which have the characteristic Apatosaurus lamination
indicate conclusively that the specimen under consideration
belongs to the genus Apatosaurus.”
“Apatosaurus” minimus
holotype AMNH 675,
sacrum in right lateral view.
“Apatosaurus” minimus holotype AMNH 675, sacrum in left lateral view.
Real?
Fabricated?
“Apatosaurus” minimus holotype AMNH 675, left ischium in medial view.
“Apatosaurus” minimus holotype
AMNH 675, left ischium in posterior view.
“Apatosaurus” minimus
holotype AMNH 675,
left ischium
“Apatosaurus” minimus
holotype AMNH 675,
incomplete right
ischium
“Apatosaurus” minimus
holotype AMNH 675,
partial left pubis
“True medial”
“Apatosaurus” minimus
holotype AMNH 675,
Composite pelvis
“Apatosaurus” minimus
holotype AMNH 675,
Composite pelvis
Slightly foreshortened,
But effect is not great.
e.g. inclined inward 20°
cos(20°) = 0.94
So orthogonal length is 94%
“Apatosaurus” minimus
holotype AMNH 675,
Composite pelvis
Out of proportion.
Is the association
good?
Slightly foreshortened,
But effect is not great.
e.g. inclined inward 20°
cos(20°) = 0.94
So orthogonal length is 94%
Is it Apatosaurus?
“The species cannot belong to Apatosaurus ... The ilia are low,
and their preacetabular processes are directed strongly
laterally somewhat as in the titanosaurids.”
– McIntosh 1990a (The Dinosauria, 1st ed.)
“From the shape of the distal end of the ischium and various
sacral characters, particularly the height of the neural
spines, it is now clear that this animal is not Apatosaurus,
and also must be excluded from the Diplodocidae.”
– McIntosh 1990b:59
“The pubis has an ischial articular surface whose length is
nearly 50% of the length of this element, a derived condition
in Camarasauromorpha (one of several features distinguishing
“A.” minimus from Apatosaurus at the generic or higher
taxonomic levels). ... This form is perhaps a basal macronarian
or basal camarasauromorph.”
– Upchurch et al. 2004 (The Dinosauria, 2nd ed.)
Is it Apatosaurus?
“The species cannot belong to Apatosaurus ... The ilia are low,
and their preacetabular processes are directed strongly
laterally somewhat as in the titanosaurids.”
– McIntosh 1990a (The Dinosauria, 1st ed.)
“From the shape of the distal end of the ischium and various
sacral characters, particularly the height of the neural
spines, it is now clear that this animal is not Apatosaurus,
and also must be excluded from the Diplodocidae.”
– McIntosh 1990b:59
“The pubis has an ischial articular surface whose length is
nearly 50% of the length of this element, a derived condition
in Camarasauromorpha (one of several features distinguishing
“A.” minimus from Apatosaurus at the generic or higher
taxonomic levels). ... This form is perhaps a basal macronarian
or basal camarasauromorph.”
– Upchurch et al. 2004 (The Dinosauria, 2nd ed.)
“Apatosaurus” minimus
Apatosaurus excelsus
“Apatosaurus” minimus
Diplodocus carnegii
“Apatosaurus” minimus
Dicraeosaurus hansemanni
“Apatosaurus” minimus
Haplocanthosaurus priscus
“Apatosaurus” minimus
Camarasaurus lentus (subadult)
“Apatosaurus” minimus
Giraffatitan brancai
“Apatosaurus” minimus
Rapetosaurus krausei
“Apatosaurus” minimus
Mamenchisaurus hochuanensis
Seems to be something new
McIntosh 1990a (Dinosauria, 1st ed.)
Fig. 16.13: comparison of ilia
Tall, narrow neural spines on wide sacrum
Sacral plates do not extend to ilium
“Turtle-mimic” rugosities on sacral plates
“Turtle-mimic” rugosities on sacral plates
Long, low ilium
Ilium vertical even while flaring.
Lateral “shelf” on bottom of ilium
Lateral “shelf” on bottom of ilium
Pubic
Pubic peduncle
peduncle
Lateral foramina (“pleurocoels”) absent
from S1 and S6
Mike: We have an identification problem
Mike: We have an identification problem
Matt: Let's use cladistics!
Mike: We have an identification problem
Matt: Let's use cladistics!
Mike: Now we have two problems.
Analysis of Taylor (2009) after Harris (2006)
Strict consensus
of 107 MPTs
Analysis of Taylor (2009) after Harris (2006)
Strict consensus
of 107 MPTs
Neosauropoda in
Big polytomy
Macronaria dissolved
Analysis of Taylor (2009) after Harris (2006)
Strict consensus
of 107 MPTs
Neosauropoda in
Big polytomy
Macronaria dissolved
Brachiosauridae
Rebbachisauridae
Flagellicaudata
Analysis of Taylor (2009) after Harris (2006)
50% majority rule consensus
of 107 MPTs
Analysis of Taylor (2009) after Harris (2006)
50% majority rule consensus
of 107 MPTs
Neosauropoda back
in shape
Analysis of Taylor (2009) after Harris (2006)
50% majority rule consensus
of 107 MPTs
Neosauropoda back
in shape
85 trees (79%)
Is “Apatosaurus” minimus a saltasaurid?
It's an appealing idea.
Would be first Morrison titanosaur
Is “Apatosaurus” minimus a saltasaurid?
It's an appealing idea.
Would be first Morrison titanosaur
Saltasaurus
Photo by Randy Irmis
Is “Apatosaurus” minimus a saltasaurid?
Opisthocoelicaudia zdanskyi
Is “Apatosaurus” minimus a saltasaurid?
Opisthocoelicaudia zdanskyi
Is “Apatosaurus” minimus a saltasaurid?
Opisthocoelicaudia zdanskyi
Analysis of Taylor (2009) after Harris (2006)
50% majority rule consensus
of 107 MPTs
Analysis of Taylor (2009) after Harris (2006)
50% majority rule consensus
of 107 MPTs
On changing one
questionable character
Analysis of Whitlock (2011)
Strict consensus of 3 MPTs
Only polytomy is within
Diplodocinae
Analysis of Whitlock (2011)
Strict consensus of 3 MPTs
Basal diplodocoid
(sister to Flagellicaudata)
Only polytomy is within
Diplodocinae
Analysis of Whitlock (2011)
Strict consensus of 3 MPTs
But only a tiny sample
of macronarians
Basal diplodocoid
(sister to Flagellicaudata)
Only polytomy is within
Diplodocinae
Back to analysis of Taylor (2009)
50% majority rule consensus
of 107 MPTs
85 trees (79%)
Back to analysis of Taylor (2009)
50% majority rule consensus
of 107 MPTs
Other MPTs
85 trees (79%)
Interim conclusion
Cladistics is no substitute
for actual palaeontology.
Key split: Diplodocoidea vs. Macronaria
Diplodocoidea
Macronaria
It's a diplodocoid!
Neural spines tall, narrow, laminated as in
diplodocoids
Neural spines tall, narrow, laminated as in
diplodocoids
Neural spines laminated as in diplodocoids
Distal end of right ischium
'V'-shaped distal articulation of ischia
It's a macronarian!
Six fully fused sacrals connecting to ilium
Ilium without distal expansion
Diplodocus sacrum AMNH 3532, anterior
Diplodocus sacrum AMNH 3532, anterior
“Apatosaurus” minimus and Diplodocus sacra
“Apatosaurus” minimus and Diplodocus sacra
“Apatosaurus” minimus and Diplodocus sacra
“A.” minimus and Apatosaurus sacra
Apatosaurus parvus
sacrum and fused ilia
(Gilmore 1936: fig. 31)
Do not mess with Gilmore.
GILMORE SAYS
REJECT WITHOUT REVIEW.
Apatosaurus ajax “Tokyo specimen”
“Apatosaurus” minimus
Diplodocus
Tokyo Apatosaurus ajax
Apatosaurus parvus
Nearly at the conclusions ...
1. “Apatosaurus” minimus ain't Apatosaurus.
2. In fact, it's not any known sauropod.
3. Heck if we know what it is.
Sauropod diversity still underestimated
Underestimated even in the Morrison
Sauropod diversity still underestimated
Underestimated even in the Morrison
Sauropod diversity still underestimated
Just like it's underestimated in the Early Cretaceous North America
+ Yellow Cat camarasaur (Britt?)
+ Yellow Cat brachiosaur (Britt?)
+ Yellow Cat titanosaur (Britt?)
+ Long Walk brachiosaur (Tidwell?)
+ CEU brachiosaur (Burge? Bird?)
+ Cloverly 2nd sauropod (D'Emic?)
Sauropod diversity still underestimated
Just like it's underestimated in the Wealden
+
+
+
+
“Pelorosaurus” becklesi
the Barnes High sauropod
a titanosaur based on good caudals
those “Eucamerotus” dorsals
etc.
Sauropod diversity still underestimated
Is it underestimated everywhere?
Is it underestimated everywhere?
Sauropod diversity still underestimated
Is it underestimated everywhere?
Is it underestimated everywhere?
… whatever Horner says.
Acknowledgements
Mark Norell and Carl Mehling
for access to the specimen.
Acknowledgements
Mark Norell and Carl Mehling
for access to the specimen.
Some sauropod genera have many species
atosaurus ajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus
osaurus lentus, ?affinis, ?africanus, ?gracilis
chiosaurus altithorax, ?brancai, ?fraasi, ?nougaredi, ?atalaiensis
marasaurus supremus, grandis, lentus, ?lewisi
lodocus longus, ?carnegii, hayi, hallorum
plocanthosaurus priscus, ?utterbacki, delfsi
ersaurus vivianae
wassea emilieae
Some sauropod genera have many species
atosaurus ajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus
osaurus lentus, ?affinis, ?africanus, ?gracilis
chiosaurus altithorax, ?brancai, ?fraasi, ?nougaredi, ?atalaiensis
marasaurus supremus, grandis, lentus, ?lewisi
lodocus longus, ?carnegii, hayi, hallorum
plocanthosaurus priscus, ?utterbacki, delfsi
ersaurus vivianae
wassea emilieae
Some sauropod genera have many species
Brontosaurus
Elosaurus
Morosaurus
Cathetosaurus
atosaurus ajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus
osaurus lentus, ?affinis, ?africanus, ?gracilis
chiosaurus altithorax, ?brancai, ?fraasi, ?nougaredi, ?atalaiensis
marasaurus supremus, grandis, lentus, ?lewisi
lodocus longus, ?carnegii, hayi, hallorum
plocanthosaurus priscus, ?utterbacki, delfsi
ersaurus vivianae
wassea emilieae
Seismosaurus
Some sauropod genera have many species
Brontosaurus
Elosaurus
Morosaurus
Cathetosaurus
atosaurus ajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus
osaurus lentus, ?affinis, ?africanus, ?gracilis
chiosaurus altithorax, ?brancai, ?fraasi, ?nougaredi, ?atalaiensis
marasaurus supremus, grandis, lentus, ?lewisi
lodocus longus, ?carnegii, hayi, hallorum
plocanthosaurus priscus, ?utterbacki, delfsi
ersaurus vivianae
wassea emilieae
?
Seismosaurus
Giraffatitan
Tornieria
Lusotitan
Eobrontosaurus
???
“Turtle-mimic” rugosities on sacral plates
“Turtle-mimic” rugosities on sacral plates
Lateral “shelf” on bottom of ilium
Lateral “shelf” on bottom of ilium