Michael P. Taylor and Mathew J. Wedel

1. 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.

3. The Morrison Formation 1.5 million km2; 9.5 million years (156.3±2 Mya to 146.8±1 Mya)

4. 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

5. 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

6. 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] Dystylosaurus edwini holotype BYU 4503 Dorsal vertebral, right anterolateral view

7. 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]

8. 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] Not yet named New diplodocoid (Vietti and Hartman 2004) AMNH diplodocine "Apatosaurus" minimus

9. Apatosaurus Apatosaurus Composite skeleton on display in public gallery at AMNH.

10. Apatosaurus has many species Apatosaurusajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus, grandis, laticollis, amplus, alanquerensis Apatosaurus (= “Brontosaurus”) excelsus holotype YPM 1980

11. Apatosaurus has many species Apatosaurusajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus, grandis, laticollis, amplus, alanquerensis Apatosaurus (= “Brontosaurus”) excelsus holotype YPM 1980

12. Apatosaurus has many species Elosaurus Brontosaurus Apatosaurusajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus, grandis, laticollis, amplus, alanquerensis Atlantosaurus montanus, immanis Apatosaurus (= “Brontosaurus”) excelsus holotype YPM 1980

13. Apatosaurus has many species Elosaurus Brontosaurus Apatosaurusajax, excelsus, lousiae, parvus, ?yahnahpin, ?minimus, grandis, laticollis, amplus, alanquerensis Camarasaurusgrandis Atlantosaurus montanus, immanis Lourinhasaurus Eobrontosaurus ??? Apatosaurus (= “Brontosaurus”) excelsus holotype YPM 1980

14. Apatosaurus species Upchurch et al. (2005) Figure 15. Specimen-level phylogenetic analysis Strict consensus

15. 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.”

16. 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.

17. 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.”

18. 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.”

19. 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.”

20. 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.”

21. 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.”

22. 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.” Not very convincing

23. “Apatosaurus” minimus holotype AMNH 675, sacrum in right lateral view.

24. “Apatosaurus” minimus holotype AMNH 675, sacrum in left lateral view.

26. Real? Fabricated?

27. “Apatosaurus” minimus holotype AMNH 675, left ischium in medial view.

28. “Apatosaurus” minimus holotype AMNH 675, left ischium in posterior view.

29. “Apatosaurus” minimus holotype AMNH 675, left ischium

30. “Apatosaurus” minimus holotype AMNH 675, incomplete right ischium

31. “Apatosaurus” minimus holotype AMNH 675, partial left pubis “True medial”

32. “Apatosaurus” minimus holotype AMNH 675, Composite pelvis

33. “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%

34. “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%

35. 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.)

36. Is it Apatosaurus? No. “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.) “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.) No.

37. “Apatosaurus” minimus Apatosaurusexcelsus

38. “Apatosaurus” minimus Diplodocus carnegii

39. “Apatosaurus” minimus Dicraeosaurus hansemanni

40. “Apatosaurus” minimus Haplocanthosaurus priscus

41. “Apatosaurus” minimus Camarasaurus lentus (subadult)

42. “Apatosaurus” minimus Giraffatitan brancai

43. “Apatosaurus” minimus Rapetosaurus krausei

44. “Apatosaurus” minimus Mamenchisaurus hochuanensis

45. Seems to be something new McIntosh 1990a (Dinosauria, 1st ed.) Fig. 16.13: comparison of ilia

46. Tall, narrow neural spines on wide sacrum

47. Sacral plates do not extend to ilium

48. “Turtle-mimic” rugosities on sacral plates

49. “Turtle-mimic” rugosities on sacral plates

50. Long, low ilium