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Appendix 1 - Taxa and Specimen Resource List

The following is a list of taxa analyzed and compared in this study, with references to descriptive papers used in the analysis of each.

Outgroup:

Lesothosaurus diagnosticus Galton, 1978–Thulborn (1970, 1972), Santa Luca (1984), Weishampel and Witmer (1990a), Sereno (1991a), Norman, (2004)

Basal Ornithopod Taxa:

Hypsilophodon foxii Huxley, 1869–Galton (1974a), Norman (2004)

Parksosaurus warreni Parks, 1926–Parks (1926), Sternberg (1940), Galton (1973)

Thescelosaurus neglectus Gilmore, 1913–Gilmore (1913), Gilmore (1915), Sternberg (1940), Galton (1974b, 1995, 1997), Norman et al. (2004)

Basal Iguanodontian Taxa:

Camptosaurus dispar (Marsh, 1879)–Marsh (1879), Gilmore (1909), Norman (2004)

Cumnoria prestwichii Hulke 1880–Hulke (1880), Galton and Powell (1980), Norman (2004)

Dryosaurus altus (Marsh, 1878)–Marsh (1878), Galton (1983), Norman (2004)

Eolambia caroljonesa Kirkland, 1998–Kirkland (1998), Head (2001), Norman (2004), McDonald et al. (2012)

Iguanodon bernissartensis Boulenger, 1881–Boulenger (1881), Norman (1980), Norman (2004)

Jinzhousaurus yangi Wang and Xu, 2001–Wang and Xu (2001), Barrett et al., (2009), Wang et al. (2011)

Mantellisaurus atherfieldensis (Hooley, 1925)–Hooley (1925), Norman (1986), Norman (2004)

Ouranosaurus nigeriensis Taquet, 1976–Taquet (1976), Norman (2004)

Tenontosaurus dossi Winkler et al., 1997–Winkler et al. (1997), Norman (2004)

Tenontosaurus tilletti Ostrom, 1970–Ostrom (1970), Forster (1990), OMNH 58340 (subadult, primary specimen), OMNH 2531 (juvenile), OMNH 16562 (subadult, skull transversely compressed, palpebral), OMNH 34191 (premaxilla)

Zalmoxes robustus (Nopcsa, 1900)–Nopcsa (1900), Weishampel et al. (2003), Norman (2004)

Hadrosauroid Taxa:

Corythosaurus casuarius Brown, 1914–Brown (1914, 1916), Ostrom (1961), Horner et al. (2004)

Edmontosaurus regalis Lambe 1917–Lambe (1917), Lull and Wright (1942), Norman (2004), Horner et al. (2004)

Probactrosaurus gobiensis Rozhdestvensky, 1966–Rozhdestvensky (1966), Norman (2002), Norman (2004)

Protohadros byrdi Head, 1998–Head (1998), Norman (2004)

Telmatosaurus transsylvanicus (Nopcsa, 1900)–Nopcsa (1900), Nopcsa (1903), Weishampel et al. (1993), Horner et al. (2004)

Appendix 2 - Character Description

The following is a list of character states used in this analysis. States were determined independently, but similarities with previously published analyses (Norman, 2004; McDonald et al., 2010) have been noted.

Facial Characters:

1. Presence of nasal contact with the maxilla and reason for exclusion of contact (Modified from Norman, 2004: Character 6):

1:0. Contact

1:1. No contact due to an anterior extension of the lachrymal

1:2. No contact due to a posterior extension of the premaxilla

2. Character of the occlusal margin of the premaxilla (Modified from McDonald et al., 2010: Character 33):

2:0. Smooth

2:1. Denticulate

2:2. Scooped, possibly to accommodate the denticles of the predentary

3. Premaxillary teeth (Modified from Norman, 2004: Character 3; McDonald et al., 2010: Character 29):

3:0. Present

3:1. Absent

4. Posterior extent of the nasal process of the premaxilla:

4:0. Does not reach antorbital fenestra

4:1. Reaches antorbital fenestra or, if no fenestra present, posterior border of dorsal process of maxilla

5. Beak position relative to tooth row (Modified from Norman, 2004: Character 2):

5:0. At level

5:1. Below

6. Width of combined frontals compared to length (Modified from Norman, 2004: Character 15):

6:0. About 2/3 length of frontal

6:1. About equal to length of frontal

6:2. Twice length of frontal

7. Transverse length of frontals' suture with parietal:

7:0. About equal with combined width of frontals

7:1. About two-thirds combined width of frontals

7:2. About half combined width of frontals

7:3. About one-third combined width of frontals

8. Frontal contribution to dorsal orbital rim (Modified from Norman, 2004: Character 16; McDonald et al., 2010: Character 68):

8:0. More than half

8:1. Less than half

8:2. Does not contribute

9. Triangular process of the parietal:

9:0. Present

9:1. Absent

10. Ratio of axial lengths of the frontal and the nasal:

10:0. Roughly equal in length

10:1. Nasal is one and one half times length of the frontal

10:2. Nasal is twice length of the frontal

10:3. Nasal is three times length of the frontal

10:4. Nasal is four times length of the frontal

11. Position of nasal contribution to the border of the external naris:

11:0. Posterodorsal border

11:1. Dorsal border

11:2. Does not contribute

12. Nature of the articulation of the nasal, frontal, and prefrontal:

12:0. Nasal overlaps frontal, overlapped by prefrontal

12:1. Nasal overlaps frontal

12:2. Nasal has transverse suture with frontal

12:3. Frontal overlaps nasal

13. Nature of the articulation of the premaxillae with the nasals:

13:0. Nasal processes wedge between nasals

13:1. Nasal overlapped by nasal process of premaxilla

13:2. Tip to tip

13:3. Nasals lie in beveled grooves in lateral surface of nasal processes of premaxilla

13:4. Nasals overlap nasal processes of premaxilla

13:5. Nasal processes split into dorsal and ventral branches, which overlap the nasals

14. Supratemporal fensestra imprints frontal:

14:0. Present

14:1. Absent

15. Lateral suture of the laterosphenoid with the:

15:0. Frontal and postorbital

15:1. Postorbital only

15:2. Frontal only

16. Rugose lateral edge of the postorbital:

16:0. Absent

16:1. Present

17. Parietal contact with the postorbital:

17:0. Present

17:1. Absent

18. Ectopterygoid articulation with the palatine:

18:0. Present

18:1. Absent

19. Ectopterygoid articulation with the jugal (Modified from Norman, 2004: Character 14; McDonald et al., 2010: Character 53):

19:0. Present

19:1. Absent

20. Jugal articulation with the quadrate:

20:0. Absent

20:1. Present

21. Ventral lobe of the jugal (Modified from Norman, 2004: Character 13; McDonald et al., 2010: Character 56):

21:0. Absent

21:1. Present

22. Jugal extends farthest posteriorly in the:

22:0. Quadratojugal process

22:1. Postorbital process

23. Accessory foramen in the quadratojugal (Modified from Norman, 2004: Character 17; McDonald et al., 2010: Character 58):

23:0. Absent

23:1. Present

24. Enclosure of the quadratojugal by the jugal:

24:0. None

24:1. Dorsal

24:2. Dorsal and ventral

25. Quadrate foramen:

25:0. Absent

25:1. Present

26. Quadratojugal size (relative to quadratojugal process of jugal):

26:0. Reduced

26:1. Large

27. Position of the contribution of the lachrymal to the orbital border:

27:0. Anteroventral corner

27:1. Anterior border

27:2. Middle anterior border

28. Contact of the nasal with the lachrymal (Modified from McDonald et al., 2010: Character 50):

28:0. Present

28:1. Absent

29. Shape of the medial lamina of the palatine:

29:0. Fan

29:1. Rectangle

29:2. Triangle

30. Maxillary tooth family count along a single side

31. Maxillary diastema:

31:0. Absent

31:1. Present

32. Lateral process of the maxilla for articulation with the jugal:

32:0. Absent

32:1. Present

33. Jugal articulation with the maxilla:

33:0. Posterior on the latter element

33:1. Displaced forward on the latter element

34. Prefrontal contact with the premaxilla (Modified from McDonald et al., 2010: Character 37):

34:0. Absent

34:1. Present

35. Position of the prefrontal contact with the nasal:

35:0. Anteromedially

35:1. Dorsally

36. Pterygoid contact with the shaft of the quadrate:

36:0. Absent

36:1. Present

37. Quadrate notch (Modified from McDonald et al., 2010: Character 61):

37:0. Absent

37:1. Present

38. Transversely wide ventral quadratic condyle (Modified from Norman, 2004: Character 18; McDonald et al., 2010: Character 64):

38:0. Present

38:1. Absent

39. “Hamalar” process of the head of the quadrate:

39:0. Absent

39:1. Present

40. Contact between paired squamosals on the midline (Modified from McDonald et al., 2010: Character 67):

40:0. Absent

40:1. Present

41. Lateral visibility of anterior process of squamosal:

41:0. Largely obscured

41:1. Prominent across intertemporal bar

Neurocranial Characters:

42. Shape of occipital condyle:

42:0. Subspherical

42:1. Flattened/reniform

43. Supraoccipital participation in the foramen magnum (Modified from McDonald et al., 2010: Character 69):

43:0. Present

43:1. Absent, due to the exoccipital

44. Shape of the cultriform process of the parasphenoid in ventral aspect:

44:0. Elongate

44:1. Triangular

45. Outline shape of the parietal in dorsal aspect:

45:0. Rectangular

45:1. Triangular

46. Ratio of length to the width of the parietal:

46:0. 1:1

46:1. 1.5:1

46:2. 1:1.5

46:3. 1:2

47. Pronounced sagittal crest of the parietal:

47:0. Absent

47:1. Present

48. Interparietal Eminence:

48:0. Present

48:1. Absent

49. Parietal/prootic contact:

49:0. Present

49:1. Absent

50. Crista prootica is comprised of:

50:0. Laterosphenoid/prootic/opisthotic

50:1. Prootic/opisthotic

Mandibular Characters:

51. Dentary diastema (Modified from Norman, 2004: Character 20; McDonald et al., 2010: Character 9):

51:0. Absent

51:1. Present

52. Posteroventral corner of the dentary extends behind coronoid process:

52:0. Absent

52:1. Present

53. Dentary symphysis:

53:0. Set level with tooth row

53:1. Set below tooth row

54. Dorsoventral borders of dentary (Modified from Norman, 2004: Character 22; McDonald et al., 2010: Character 15):

54:0. Thicker posteriorly

54:1. Parallel

54:2. Thicker anteriorly

55. Length of the dentary bearing dentition:

55:0. Full

55:1. 2/3

55:2. Half

56. Orientation of coronoid process of the mandible (Modified from Norman, 2004: Character 23; McDonald et al., 2010: Character 20):

56:0. Posteriorly deflected

56:1. Vertical

56:2. Anteriorly deflected

57. Coronoid bone:

57:0. Present

57:1. Absent

58. Presence of two processes around the Meckelian canal:

58:0. Absent

58:1. Present

59. Presence of shelf between the teeth and the coronoid process (Modified from Norman, 2004: Character 24):

59:0. Absent

59:1. Present

60. Axially flared coronoid process (Modified from McDonald et al., 2010: Character 21):

60:0. Absent

60:1. Present

61. Bifurcate ventral process of the predentary (Modified from Norman, 2004: Character 19; McDonald et al., 2010: Character 2):

61:0. Absent

61:1. Present

62. Character of the occlusal margin of the predentary (Modified from McDonald et al., 2010: Character 4):

62:0. Smooth

62:1. Denticulate

63. Lateral visibility of the angular (Modified from Norman, 2004: Character 26; McDonald et al., 2010: Character 27):

63:0. Visible

63:1. Reduced visibility

63:2. Not visible

64. Nature of articulation of the angular with the surangular (Modified from McDonald et al., 2010: Character 26):

64:0. Angular laterally overlaps surangular

64:1. Groove in ventral surangular

64:2. Angular laterally abuts surangular

65. Anterior extension of the coronoid:

65:0. Present

65:1. Absent

66. Lateral visibility of the coronoid bone:

66:0. Invisible

66:1. Largely visible

66:2. Reduced

67. Splenial coverage of the Meckelian canal:

67:0. Extensive

67:1. Posterior only

68. Presence of the prearticular:

68:0. Present

68:1. Absent

69. Number of surangular foramina (Modified from Norman, 2004: Character 25; McDonald et al., 2010: Character 24):

69:0. Two

69:1. Three

69:2. One

69:3. None

70. Nature of ridges on the teeth (Modified from Norman, 2004: Character 27; McDonald et al., 2010: Characters 85, 90, 91):

70:0. Absent

70:1. Ridge on Dentary teeth

70:2. Ridge on Dentary and Maxillary Teeth

70:3. Ridge on Maxillary with reduced Dentary ridge

70:4. Ridge on Dentary with reduced Maxillary ridge

71. Dentary tooth family count along a single side

Postcranial Characters:

Taken, with modifications, from Norman, 2004.

72. Dorsal neural spines:

72:0. Low and Square

72:1. Rectangular and height more than twice width

72:2. Extremely elongate, height more than six times width

73. Sacrum:

73:0. Seven or fewer vertebrae

73:1. More than seven

74. Scapular blade:

74:0. Straight

74:1. Curved

74:2. Curved and flared distally

75. Scapular acromion:

75:0. Prominent boss on the anterior margin of the scapula

75:1. Boss is reflected laterally

76. Humerus:scapula length:

76:0. Approximately equal lengths

76:1. Scapula longer than humerus

77. Sternal shape:

77:0. Reniform

77:1. Hatchetlike

78. Carpal structure:

78:0. Fully ossified and blocklike

78:1. Reduced

79. Metacarpal I shape:

79:0. Dumbbell-like

79:1. Short and blocklike

79:2. Absent

80. Metacarpals II-IV:

80:0. Dumbbell-like and spreading

80:1. Closely appressed

80:2. Appressed, slender and elongate

81. Manus digit I:

81:0. Present

81:1. Absent

82. Manus ungual I:

82:0. Claw-like

82:1. Conical

82:2. Absent

83. Manus unguals II and III:

83:0. Claw-like

83:1. Flattened, twisted and hoof-like

83:2. Digit II claw-like, Digit III nub

84. Manus digit III:

84:0. Four phalanges

84:1. Three phalanges

85. Preacetabular process of ilium:

85:0. Long and laterally compressed

85:1. Strongly downturned

85:2. Distally twisted

86. Dorsal margin of iliac blade:

86:0. Mostly smooth edged

86:1. Strongly notched behind the ischial peduncle

87. Dorsal edge of ilium above ischial peduncle:

87:0. Not thickened and bevelled

87:1. Thickened

87:2. Everted with pendent tip

88. Ilium, postacetabular process:

88:0. Tapering posteriorly

88:1. Low and rectangular

89. Pubis, prepubic process:

89:0. Short and blunt

89:1. Elongate

90. Pubis, prepubic process:

90:0. Rod-shaped

90:1. Laterally compressed, bar-like

90:2. Short constriction and distal expansion

90:3. Deep expansion

91. Pubic shaft:

91:0. Ends adjacent to distal end of ischium

91:1. Shorter than ischium, no pubic symphysis

92. Ischium, shaft shape:

92:0. Straight

92:1. Arched dorsally

93. Ischium shaft:

93:0. Flattened in cross section

93:1. Rounded in cross section

94. Obturator process of the ischium:

94:0. Absent

94:1. Present near midshaft

94:2. Present and close to pubic peduncle

95. Tip of ischium:

95:0. Unexpanded

95:1. Axial expansion to form a boot

96. Femur:

96:0. Distal half of shaft curved posteriorly

96:1. Straight

97. Femoral fourth trochanter:

97:0. Pendent

97:1. Triangular

97:2. Crested eminence

98. Femur extensor groove:

98:0. Open shallow trough

98:1. U-shaped groove

98:2. Partially enclosed channel

98:3. Fully enclosed tunnel

99. Femur distal condyles:

99:0. Moderately expanded posteriorly

99:1. Expanded posteriorly and anteriorly

100. Metatarsal I:

100:0. Well developed and articulates with phalanges

100:1. Slender and splintlike

100:2. Absent

101. Pedal unguals:

101:0. Elongate and pointed claws

101:1. Elongate but bluntly truncated

101:2. Short, broad and crescentic with reduced or absent claw grooves

APPENDIX 3.

The following is a matrix composed of the states coded for each of 19 ingroup taxa and one outgroup taxon analyzed for each of the characters in Appendix 2. It is available in text and Excel formats.

APPENDIX 4.

The following is a collection of three-dimensional renderings of each of the elements of the skull of OMNH 58340. They are stored as stl files, which can be easily viewed using software freely available for download on the internet (e.g., by searching for "stl file viewer"). 

APPENDIX 5.

The following is the CT data generated for use in this study. The first section (Cranium) comprises scans of the skull, without the mandibles or disarticulated pieces. The second section (Braincase) comprises scans of the braincase section of the cranium, taken at a higher resolution than those for the rest of the skull. Finally, the third section (Miscellaneous) comprises the mandibles and other disarticulated elements (e.g., the right prefrontal and the predentary). Also included are documents detailing the scanning parameters used for each set of scans.

 

 

FIGURE 1. Posterior skull schematic (above) and photograph (below) of OMNH 58340. The schematic was reconstructed by digitally mirroring the left side of the suspensorium in order to approximate the actual appearance of the skull. The two images are set to the same scale, demonstrating the amount of displacement in the right side. Anterior is into the page. Abbreviations: bp - basipterygoid process; fm - foramen magnum; ptf - posterior temporal foramen (obscured); sb - squamosal boss.

figure 1

FIGURE 2. Left lateral skull schematic (above) and left skull photograph (below) of OMNH 58340. The skull is angled at the ‘alert position’ indicated by the horizontal semicircular canal. Natural fenestrae are shaded gray. Dashed outline denotes conjectural sclerotic ring. Anterior is to the left. Abbreviation: mf - maxillary foramen.

figure 2

FIGURE 3. Photograph of the lateral side of the disarticulated right maxilla and other associated elements of OMNH 58340. The exclusion of the maxilla from contact with the nasal is apparent, although there is some separation, probably taphonomic, of the premaxilla and lacrimal. Dotted line indicates uncertain sutural placement between the nasal and maxilla.

figure 3

FIGURE 4. Ventral (4.1) and anterior (4.2) photographs of the right premaxilla of OMNH 34191. In 4.1, anterior is out of the page and lateral is left. In 4.2, lateral is to the left and anterior is up.

figure 4

FIGURE 5. Dorsal skull schematic (above) and photograph (below) of OMNH 58340. The schematic was reconstructed by digitally mirroring the left side of the rostrum and suspensorium in order to approximate the actual appearance of the skull. Dotted line at the anterior edge of the frontals indicates uncertain sutural placement. Natural fenestrae are shaded gray. Anterior is to the right.

figure 5

FIGURE 6. Ventral skull schematic (above) and photograph (below) of OMNH 58340. The schematic was reconstructed by digitally mirroring the left side of the rostrum and suspensorium in order to approximate the actual appearance of the skull. Natural fenestrae are shaded gray. Anterior is to the right. Abbreviations: bt - basal tubera of the basisphenoid; lt - lateral tubercle of the basioccipital; mt - median tubercle of the basioccipital; ? - possible second lateral tubercle of the basioccipital.

figure 6

FIGURE 7. Strict component consensus tree of selected members of Ornithopoda included in this analysis. Lesothosaurus diagnosticus is the outgroup. Bremer support values are located below, while Bootstrap and Group Present/Contradicted (GC) support values are located above the branches immediately preceding the node to which they refer. GC values are in bold. Certain nodes are noted with letters referenced in the text. Optimization was performed in PAUP* version 4.0b10 (Swofford, 2002) and checked in TNT (Goloboff et al., 2008).

figure 7

FIGURE 8. Coronal CT image, taken at the level of the open naris, of the left premaxilla (green, left), maxilla (pink, middle), and the vomer (cream, bottom) of OMNH 58340 showing the nature of their articulation. The maxilla likely fitted in closer articulation with the premaxilla. Faint green lines are an artifact of the program used to define the element on each image. Anterior is into the page.

figure 8

FIGURE 9. Medial skull schematic (above), right skull photograph (middle), and right skull schematic (below) of OMNH 58340. Parts of the vomer, frontal, parietal, laterosphenoid, squamosal, supraoccipital, exoccipital/opisthotic, and prootic, as well as the entirety of the right quadrate, quadratojugal, and jugal, have been removed from the medial skull schematic in order to show the structure of the braincase and its orientation with the rest of the skull. The broken texture in gray in the upper schematic indicates the sectioning of elements necessary to view the endocranium. The skull is angled at the ‘alert position’ indicated by the horizontal semicircular canal. Natural fenestrae are shaded gray. Anterior is to the right. Abbreviations: ap - alveolar parapet; s - sulcus.

figure 9

FIGURE 10. Medial view of the left side of the virtual skull of OMNH 58340 with the vomer present (10.1), allowing a view of the articulation of the vomer with the pterygoid, and with the palatine and vomer removed (10.2), allowing a view of the joints between the maxilla, lacrimal, prefrontal, jugal, ectopterygoid, and pterygoid. The vertically striated texture present on the visible surfaces of many elements, notably the lacrimal, maxilla, and premaxilla, is an artifact of the process used to isolate CT images of each element from the remainder of the data set. Abbreviations: f - flange; pp - posterior processes; tp - triangular processes.

figure 10

FIGURE 11. Photographs of the medial aspect of the vomer (foreground) and dental ridge of the maxilla (background, just below matrix) of OMNH 58340 (11.1) and showing the fine grain on the dorsal surface of the maxilla (11.2). Single headed arrow indicates the median ridge of the vomer. Double headed arrows indicate the paired sharp ridges of the same element. The area figured in 11.2 is indicated by the shaded area in 11.1. Anterior is to the right.

figure 11

FIGURE 12. Coronal CT image, taken at the level of the posterior termination of the antorbital fenestra, of the paired posterior processes of the vomer of OMNH 58340. This image shows the disarticulated nature of the two halves of the posterior part of the element, as well as their shape just anterior to the opening of the orbit, between the paired palatines. Faint green lines are an artifact of the program used to define the element on each image. Anterior is into the page.

figure 12

FIGURE 13. Medial (13.1) and ventral (13.2) photographs of the disarticulated right palatine of OMNH 58340. Anterior is to the left. Abbreviations: ap - anterior process; apt - articulation with pterygoid; l - lamina; lp - lateral process.

figure 13

FIGURE 14. Dorsal view of the elements of the virtual palate of OMNH 58340, including the palatine, maxilla, pterygoid, and ectopterygoid, as well as the jugal, detailing the means of articulation between the various elements. Anterior is to the right.

figure 14

FIGURE 15. Posterolaterodorsal view of the left orbit of the virtual skull of OMNH 58340, presenting a view of the joint between the prefrontal, lacrimal, jugal, and palatine. The parallel contour lines on the posterior surfaces of the parietal, prefrontal, quadrate, and squamosal, are an artifact of the CT scanning process, and represent the faces of individual slice images. These lines occur on any surface angled near parallel with the scanner. Anterior is into the page, toward the top left. Abbreviation: lt - lateral tubercle; pg - pterygoid groove.

figure 15

FIGURE 16. Lateral view (16.1) of the virtual ectopterygoid (green) and pterygoid (yellow) of OMNH 58340. Dorsal view (16.2) of the virtual pterygoid only. Anterior is to the left. Abbreviations: ep - ectopterygoid process; lf - lateral fossa; pf - pterygoid flange; pp - palatine process; mp - medial process; qp - quadratic process.

figure 16

FIGURE 17. Anteromediodorsal view of the virtual skull of OMNH 58340, showing the features surrounding the maxillary groove of the maxilla, including the dental ridge and the possibility of a soft-tissue roof covering it in life. Abbreviations: dr - dental ridge of the maxilla; la - lamina of the maxilla; mf - medial flange of the lacrimal; mg - maxillary groove; mp - maxillary projection.

figure 17

FIGURE 18. Anterior skull schematic (above) and photograph (below) of OMNH 58340. The two images are set to the same scale, demonstrating the amount of displacement in the right side of the skull. The schematic was reconstructed by digitally mirroring the left side of the rostrum and suspensorium in order to approximate the actual appearance of the skull. Natural fenestrae are shaded gray. Anterior is out of the page.

figure 18

FIGURE 19. Medial view of the virtual left premaxilla, nasal, lacrimal, and maxilla of OMNH 58340 showing the nasal arch of the nasal just below its articulation with the nasal process of the premaxilla. Anterior is to the right. Abbreviation: na - nasal arch.

figure 19

FIGURE 20. Coronal CT image, taken at the anterior edge of the left orbit, of the prefrontal (violet), nasal (dark green), and frontal (yellow) of OMNH 58340 showing their articulation. Faint green lines are an artifact of the program used to define the element on each image. Anterior is into the page.

figure 20

FIGURE 21. Ventral view of the skull roof of OMNH 58340. The palate and the lateral facial elements have been removed to allow for the viewing of the associations of the elements depicted. Location of endocast indicated by black outline. Note the nasal and prefrontal ending at nearly the same point posteriorly. Anterior is to the right. Abbreviations: la - area of articulation with capitate process of laterosphenoid; pp - pedicles of partietal; ar - arcuate ridge; sa - area of articulation with supraoccipital.

figure 21

FIGURE 22. Coronal CT image of the left maxilla (pink) of OMNH 58340, taken midway along the axial length of the element, showing its facial lamina (left) and dental ridge (right, surrounding two teeth, lighter, due to higher density). Faint green lines are an artifact of the program used to define the element on each image. Abbreviations: a - alveolus; c - canal; lg - lamellar gap.

figure 22

FIGURE 23. Labial photograph of the left maxillary dentition (23.1) and lingual photograph of the left dentary dentition (23.2) of OMNH 58340. Note the finely ornamented surface of the alveolar parapet of the dentary between the lower exposed surfaces of the teeth and the dorsally arched sulcus.

figure 23

FIGURE 24. Coronal CT image, taken just anterior of the left orbit, of the lacrimal (light blue) and its shelf (lower right) of OMNH 58340. Faint green lines are an artifact of the program used to define the element on each image. Anterior is into the page.

figure 24

FIGURE 25. Ventral (25.1) and medial (25.2) photographs of the disarticulated right prefrontal of OMNH 58340. Anterior is left. Arrows indicate undulating texture on the ventral and medial surfaces of the element, which indicate the area of articulation with the frontal. The space between two broken ends of the ventral process in 25.2 is indicated by a dashed gray line. Abbreviation: vp - ventral process.

figure 25

FIGURE 26. Photograph of the left prefrontal, frontal, and postorbital of OMNH 58340, showing the high degree of rugosity above the orbit. Anterior is to the left.

figure 26

FIGURE 27. Photograph of the prefrontal fossa (indicated by arrows) of the right frontal of OMNH 58340. The pyramidal corner of the disarticulated prefrontal fits into this fossa. Anterior is to the right and out of the page.

figure 27

FIGURE 28. Coronal CT image, taken just anterior of the orbit, of the left prefrontal and its ventral process (violet), lacrimal (light blue), and palatine and its lateral process (brown) of OMNH 58340 showing the nature of their articulation. Faint green lines are an artifact of the program used to define the element on each image. Anterior is into the page.

figure 28

FIGURE 29. Photograph of the left squamosal of OMNH 58340, showing the deep texture on the lateral surface of the body of the bone, continued forward onto the lateral surface of the squamosal process of the postorbital. Anterior is to the upper left and into the page. Abbreviations: vt - ventral tab of the squamosal.

figure 29

FIGURE 30. Lateral view of the virtual left squamosal of OMNH 58340 showing the deep articular fossae and the processes of the element. Anterior is to the left. Abbreviations: ap - anterior process; ah - articulation for head of quadrate; apo - articulation for postorbital; poq - postquadratic process; preq - prequadratic process.

figure 30

FIGURE 31. Lateral view of the virtual left quadratojugal of OMNH 58340 showing the rhomboidal shape of the element. The corrugated area on the left half of the element (outlined in black) is an artifact of the sectioning process and represents the articular surface for the jugal. Anterior is to the left.

figure 31

FIGURE 32. A lateral view of the virtual skull (lower left) and braincase (inlay, upper right) of OMNH 58340 with a high transparency, making the endocast (blue), cranial nerves (yellow), and semicircular canals (magenta) visible. The skull is at the ‘alert position’ indicated by the horizontal semicircular canals. Abbreviations: bt - basal tubera; bpt - basipterygoid process; oc - occipital condyle.

figure 32

FIGURE 33. Photograph of the posterior portion of the dorsal surface of the skull of OMNH 58340, showing the small waist of the parietal (indicated by arrow). This groove may have been for the passage of an artery or may mark the separation between two muscles. There is an identical feature on the opposite side of the skull. Anterior is to the left.

figure 33

FIGURE 34. Anterior view of the virtual braincase of OMNH 58340. The supraoccipital is indicated by the pink that shows through the foramina for CN I–III. The smooth area across the front of the parasphenoid and the left basipterygoid process, as well as the regular curvature of the outer edge of the right laterosphenoid, prootic, and opisthotic (to the left), are artifacts of CT scanning and represent the limits of the data set. Note the irregular anterior surface of the parietal, showing the interdigitate nature of the suture of that element with the frontals. Black lines are used to denote particular features. Anterior is out of the page and ventral is down. Abbreviations: bt - basal tubera; bpt - basipterygoid process; ct - crista terminalis; eV - excavation for trigeminal nerve (CN V); hf - hypophysial fossa; pp - preotic pendant; st - sella turcica; vt - ventral tubercle of the orbitosphenoid.

figure 34

FIGURE 35. Lateral view of the virtual braincase of OMNH 58340. Black lines are used to denote particular features. The straight lines at the front of the basisphenoid to the left and the exoccipital/opisthotic to the right are artifacts of the CT scanning and represent the limits of the data set. The frontal and parietal extend beyond these levels because they were transplanted from the full cranial scan. Note that the basioccipital is visible in two locations. Anterior is to the left. Abbreviations: bt - basal tubera; bpt - basipterygoid process; cc - internal carotid canal (obscured); ci - crista interfenestralis; cm - crista metotica; cp - crista prootica; ct - crista tuberalis; eV - excavation for trigeminal nerve (Cranial Nerve V); fm - fenestra metotica; fo - fenestra ovalis; g - groove of crista tuberalis; pp - preotic pendant; sr - stapedial recess; ? - unnamed ridge.

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FIGURE 36. Dorsolateral view of the virtual braincase of OMNH 58340 with the parietal, left laterosphenoid, left prootic, and left sections of the supraoccipital and exoccipital/opisthotic removed. The flat edges of the parasphenoid and of the supraoccipital and exoccipital to the left and right, respectively, are artifacts of the CT scanning, and represent the limits of the data set. The supraoccipital (pink), exoccipital (brown), and orbitosphenoid (light green) were sectioned to allow for viewing of structures that would normally be covered by these elements. The computer program used to do this randomly assigns interior colors to the models, hunter green in the case of the supraoccipital, light blue in the case of the exoccipital, and maroon for the orbitosphenoid. Anterior is to the left. Abbreviations: bpt - basipterygoid process; dVIII - dorsal ramus of the acoustic nerve; ed - endolymphatic duct; mp - median process of the basioccipital; pf - area of the pontine flexure; vp - ventral process of the supraoccipital; vVIII - ventral ramus of the acoustic nerve.

figure 36

FIGURE 37. Posterior view of the virtual braincase of OMNH 58340 with the exoccipital/opisthotic removed. The regularly curved borders along the right side, as well as the flat squamosal bosses of the supraoccipital, are an artifact of the CT scanning and represent the limits of the data set. Anterior is into the page and dorsal is up. Abbreviations: ab - auditory bulla; ap - ascending process; bf - basioccipital furrow; bt - basal tubera; bpt - basipterygoid process; dt - dorsal tubercle; ns - nuchal shelf; sb - squamosal boss; ss - supraoccipital shelf; vp - ventral processes.

figure 37

FIGURE 38. Lateral view of the virtual supraoccipital (purple) and the left endosseous labyrinth (pink) of OMNH 58340 showing the common crus of the semicircular canals entering the ventral process of the supraoccipital. Anterior is to the left. Abbreviations: asc - anterior semicircular canal; cc - common crus; nc - nuchal crest; psc - posterior semicircular canal; ss - supraoccipital shelf; vp - ventral process.

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FIGURE 39. Dorsal view of the virtual braincase of OMNH 58340 with the parietal removed, showing the composition of the floor of the braincase. The straight posterior edge of the opisthotic, as well as the straight anterior edge of the basisphenoid and lateral edge of the laterosphenoid, are artifacts of the CT scanning and represent the limits of the data set. Anterior is down. Abbreviations: ap - area of articulation with parietal; i - infundibular canal; pp - posterior process of the orbitosphenoid.

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FIGURE 40. Horizontal CT image, taken at the level of the trigeminal foramina, of the basisphenoid and parasphenoid (orange), laterosphenoids (pink and light blue), trigeminal nerve foramina (yellow), prootics (teal and red), horizontal semicircular canals (purple), and exoccipital/opisthotic (green) of OMNH 58340. The endocast is the black and gray area in the middle of the image. The ventral processes of the supraoccipital can also be seen, as well as their peculiar density. Faint green lines are an artifact of the program used to define the element on each image. Anterior is down. Abbreviations: sc - horizontal semicircular canals; vp - ventral processes.

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FIGURE 41. Anterior view of the virtual braincase of OMNH 58340 with the parietal, orbitosphenoid, left laterosphenoid, and basisphenoid/parasphenoid removed. The curvature along the left border is an artifact of the CT scanning and represents the limit of the data set. Black lines are used to denote particular features. Anterior is out of the page and ventral is down. Abbreviations: conical fossa; ds - dorsal sagittal sinus; fm - foramen magnum.

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FIGURE 42. Posterodorsal view of the virtual braincase of OMNH 58340 with the parietal, supraoccipital, and exoccipital/opisthotic removed and the paths of the cranial nerves highlighted. Anterior is into the page. Abbreviations: i - infundibulum; mp - median process.

figure 42

FIGURE 43. Photograph of the parasphenoid and basisphenoid complex and the anterior braincase of OMNH 58340. The parasphenoid extends forward (right) from the body of the basisphenoid and, at this angle, disappears behind the displaced right posterior process of the vomer. The trench running along the dorsal surface of the parasphenoid is visible (indicated by arrows). The ventral outline of the preotic pendant is indicated by the dashed line. Anterior is to the right and out of the page. Abbreviations: ct - possible crista trabecularis; pp - preotic pendant.

figure 43

FIGURE 44. Right lateral (44.1), anteroventral (44.2), anterior (44.3), and posterior (44.4) views of the virtual endocast of OMNH 58340. 44.1 shows various landmarks for the passage of venous sinuses and cranial nerves. 44.2 highlights the waists between the cerebrum and cerebellum anterodorsally and the cerebellum and medulla posteroventrally. 44.3 shows the faint lobes present on the dorsal surface of the endocast, separated by a small trough (indicated by arrow). 44.4 shows the dorsal sagittal sinus in the middle and the flocculi of the endocast, as well as the dorsal bulbous expansions. Abbreviations: ad - anterodorsal ridge; av - anteroventral ridge; be - bulbous expansions; die - diencephalon; ds - dorsal sagittal sinus; dvs - dorsal venous sinus; f - flocculus; i - beginning of infundibular stalk; mes - mesencephalon; met - metencephalon; my - myelencephalon; pi - pineal process; pro - prosencephalon; rho - rhombencephalon; rV - ridge running to trigeminal nerve (CN V); rVI - ridge running to abducens nerves (CN VI) tel - telencephalon.

figure 44

FIGURE 45. Dorsal (45.1), right lateral (45.2), anterior (45.3), and posterior (45.4) views of the virtual endosseous labyrinths of OMNH 58340. The canals are oriented in 45.1 such that anterior is above and posterior below. Ventral is down in all other images. Abbreviations: aa - anterior ampulla; asc - anterior semicircular canal; au - anterior utricle; ca - cavum capsularis; cc - common crus; fo - fenestra ovalis; lr - lagenar recess; lsc - lateral semicircular canal; pa - posterior ampulla; psc - posterior semicircular canal; pu - posterior utricle; v - vestibule.

figure 45

FIGURE 46. Lateral schematic of the left (above) and photographs of the left (middle) and right (below) mandibles of OMNH 58340. Note the amount of dorsoventral compression of the right mandible when compared with the left. Anterior is to the left in the first two images and to the right in the third. Abbreviation: sf - surangular foramen.

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FIGURE 47. Medial schematic of the left (above) and photographs of the left (middle) and right (below) mandibles of OMNH 58340. Note the amount of dorsoventral compression of the right mandible when compared with the left. Anterior is to the right in the first two images and to the left in the third. Abbreviations: ap - alveolar parapet; imc - internal mandibular foramen; mc - Meckelian canal.

figure 47

FIGURE 48. Photographs of the predentary of OMNH 58340 in dorsal (48.1), anterior (48.2), lateral (48.3), posterior (48.4), and ventral (48.5) views. Abbreviations: dp - dentary process; mt - median tab; pd - primary denticle; vp - ventral process; vs - ventral sulcus.

figure 48

FIGURE 49. Dorsal (49.1), lateral (49.2), and medial (49.3) views of the virtual left dentary of OMNH 58340, disarticulated. Anterior is to the left in the first two images and to the right in the third. Abbreviations: at - alveolar trench; au - alveolar undulations; ca - area for articulation with coronoid; Mc - Meckelian canal; pf - predentary foramina; sa - area for articulation with surangular.

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FIGURE 50. Lateral (50.1) and medial (50.2) views of the disarticulated virtual left coronoid of OMNH 58340. The parallel texturing covering most of 50.1 is an artifact of the sectioning process used to isolate the element and represents the articular surface for the surangular and dentary. Anterior is left in 50.1 and right in 50.2. Abbreviations: ap - anterior process; cp - coronoid process; da - articular surface for dentary; sa - articular surface for surangular; vt - ventral tab.

figure 50

FIGURE 51. Medial view of the virtual left mandible of OMNH 58340 with the splenial and prearticular removed to show the extent of the Meckelian canal as it traverses the mandible. Anterior is right. Abbreviation: mc - Meckelian canal.

figure 51

FIGURE 52. Lingual (above) and labial (below) views of the complete virtual tooth set of the left dentary of OMNH 58340, demonstrating the method of replacement, with groups of teeth beginning to be replaced in alternating succession from posterior to anterior. Individual Zahnreihen are indicated by dots of the same color placed at the occlusal tips of the teeth. Anterior is to the left in the upper image and to the right in the lower image.

figure 52

FIGURE 53. Lateral view of the virtual left splenial of OMNH 58340, disarticulated. Anterior is left. Abbreviations: ar - axial ridge; dp - dorsal process; imf - internal mandibular foramen; pr - posterior ridge.

figure 53

FIGURE 54. Lateral (54.1) and medial (54.2) views of the virtual left angular of OMNH 58340. Anterior is left in the upper image and right in the lower image. Abbreviations: da - articular surface for the dentary; mr - medial ridge; vr - ventral ridge.

figure 54

FIGURE 55. Medial view with the dorsal tip rotated lingually (55.1) of the virtual left angular (blue) and surangular (pink) and medial view (55.2) of the disarticulated virtual left surangular of OMNH 58340. Anterior is to the right. Abbreviations: aa - anterior angle; aw - anterior wing; da - dorsal angle; sf - surangular foramen; rp - retroarticular process; va - ventral angle.

figure 55

FIGURE 56. Photograph of the articular surface of the left mandible of OMNH 58340, detailing the facets present on the dorsal surfaces of the surangular and prearticular. The dashed lines circumscribe the articular fossae of the prearticular. Anterior is up. Abbreviations: lf - lateral articular fossa; m - matrix; mf - medial articular fossa.

figure 56

FIGURE 57. Dorsal schematic of the left (above) and photographs of the left (middle) and right (below) mandibles of OMNH 58340. Anterior is to the right. Abbreviation: df - dental foramina.

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FIGURE 58. Posterodorsal view (58.1) of the virtual left surangular (pink) and prearticular (green) and medial view (58.2) of the virtual left prearticular of OMNH 58340. The left image shows the nature of the articulation of the two elements at the point of articulation of the mandible with the quadrate (indicated by arrow). Anterior is into the page in 58.1 and to the right in 58.2. Abbreviations: ap - anterior process; rp - retroarticular process; sa - area of articulation with the splenial.

figure 58

FIGURE 59. Ventral schematic (above) and photographs of the right (middle) and left (below) mandibles of OMNH 58340. Anterior is to the left.

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FIGURE 60. Coronal CT images of the maxillary (above) and dentary (below) teeth, taken midway along the length of the respective elements, of OMNH 58340 showing the method of lingual replacement and the concurrent resorption of the tooth being replaced. Dorsal is up and anterior is into the page. Abbreviations: ca - carina; ci - cingulum; e - enamel.

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FIGURE 61. Photograph of the left (above, in lingual view) and right (below, in buccal view) hyoids of OMNH 58340. Anterior is to the left in the upper image and to the right in the lower image.

figure 61

FIGURE 62. Optimized character distribution showing unambiguous character state changes on one of 12 most parsimonious trees (MPTs) recovered in this analysis. Character number and state present are indicated by the number above and below each line, respectively. Synapomorphic character states are indicated by black circles, while white circles denote homoplastic character states. Certain nodes are noted with letters referenced in the text. Optimization was performed in PAUP* version 4.0b10 (Swofford, 2002) and checked in TNT (Goloboff et al., 2008).

figure 62

 
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The cranial anatomy of Tenontosaurus tilletti Ostrom, 1970 (Dinosauria, Ornithopoda)

D. Andrew Thomas

Plain Language Abstract

Tenontosaurus tilletti is a species of ornithopod, a two-legged herbivore related to the duck-billed dinosaurs, from the Lower Cretaceous (120–110 m.y.a.). Previous descriptions of the anatomy of the species have consisted exclusively of a short account of specimens collected in the Cloverly Formation of the Bighorn Basin of Montana, as well as a more detailed description of the postcranial skeleton. To date, the skull of T. tilletti remains poorly described. The present study is an attempt to rectify the situation using Tenontosaurus tilletti material collected from southeastern Oklahoma. In particular, an especially well preserved skull (OMNH 58340) of T. tilletti was CT-scanned and virtually separated into its individual skull bones. These elements, as well as reconstructions of the internal spaces for soft tissues, such as the braincase and cranial nerve passages, are described and illustrated in detail. This description is used to conduct a new analysis of the relationships of Tenontosaurus with its fellow ornithopods. The analysis strongly supports the genus Tenontosaurus, which includes another species, T. dossi from Texas, as well as its position relative to more basal ornithopods and derived iguanodontians. This new analysis largely agrees with previous studies.

Resumen en Español

La anatomía craneal de Tenontosaurus tilletti Ostrom, 1970 (Dinosauria, Ornithopoda)

Tenontosaurus tilletti Ostrom, 1970, históricamente asignado a 'Iguanodontia basales', es una especie de herbívoro bípedo del Cretácico Temprano (Aptiano–Albiano). Las publicaciones previas sobre la anatomía de la especie han consistido de breves informes de especímenes colectados en la Formación Cloverly de la Cuenca Bighorn de Montana, y una descripción más detallada del esqueleto postcraneal hecha por Forster (1990). Al día de hoy, el cráneo de T. tilletti permanece pobremente descripto debido a falta de investigación y especímenes mal preservados.

El presente estudio es un intento de rectificar la situación con material referible a Tenontosaurus tilletti, colectado en el sudeste de Oklahoma. Un cráneo particularmente bien preservado (OMNH 58340) de T. tilletti fue escaneado mediante TC y se aislaron sus elementos constituyentes. Estos elementos, así como las reconstrucciones de los espacios internos ocupados por tejidos blandos, tales como el endomolde y forámenes de nervios craneales, son aquí descriptos e ilustrados en detalle. Esta descripción se utiliza para conducir un análisis sistemático novedoso. El análisis respalda al género Tenontosaurus, así como a su posición relativa respecto de los 'hipsilofodontes' y los iguanodontianos, y coincide en gran parte con análisis previos.

Palabras clave: anatomía craneal; descripción; tomografía computarizada (TC); ornitópodo; Iguanodontia; Tenontosaurus

Traducción: Diana Elizabeth Fernández

Résumé en Français

L'anatomie crânienne de Tenontosaurus tilletti Ostrom, 1970 (Dinosauria, Ornithopoda)

Tenontosaurus tilletti Ostrom, 1970, historiquement attribué aux "Iguanodontia basaux", est une espèce de dinosaure herbivore bipède du Crétacé inférieur (Aptien-Albien). Les publications précédentes sur l'anatomie de cette espèce comprennent un bref rapport sur les spécimens collectés dans la formation de Cloverly du bassin du Bighorn dans le Montana et une description plus détaillée du squelette post-crânien par Forster (1990). Jusqu'à présent, le crâne et la mandibule de T. tilletti sont encore mal décrits, et ce en raison du peu de recherches qui leur sont consacrées et de la mauvaise préservation des spécimens.

Cette étude tente de rectifier la situation en décrivant du matériel attribué à Tenontosaurus tilletti, collecté au sud-est de l'Oklahoma. Un spécimen de T. tilletti, comprenant le crâne et la mandibule associés et particulièrement bien préservés (OMNH 58340), a notamment été scanné par tomographie assistée par ordinateur et les éléments le composant ont été séparés virtuellement. Ces éléments, ainsi que la reconstruction des espaces internes abritant les tissus mous, tels que le moulage endocrânien et les foramens des nerfs crâniens, sont ici décrits et illustrés en détail. Cette description est utilisée pour effectuer une nouvelle analyse phylogénétique. Cette dernière soutient fortement la monophylie du genre Tenontosaurus, de même que sa position relativement aux autres Iguanodontia et aux 'hypsilophodontes', et est en grande partie en accord avec les analyses précédentes.

Mots-clés : anatomie crânienne ; description ; tomographie assistée par ordinateur (CT) ; ornithopode ; Iguanodontia ; Tenontosaurus

Translator: Antoine Souron

Deutsche Zusammenfassung

Die Cranial-Anatomie von Tenontosaurus tilletti Ostrom, 1970 (Dinosauria, Ornithopoda)

Tenontosaurus tilletti Ostrom, 1970, historisch den 'basalen Iguanodontia' zugeordnet, ist eine Art bipeder Herbivoren aus der unteren Kreide (Apt–Alb). Vorangehende Veröffentlichungen zur Anatomie dieser Art bestanden aus einem oberflächlichen Bericht über die Stücke aus der Cloverly Formation des Bighorn Beckens von Montana ebenso wie aus einer detaillierteren Beschreibung des Postcranialskeletts von Forster (1990). Bis heute verbleibt der Schädel von T. tilletti wegen fehlender Untersuchungen und schlecht erhaltener Stücke unzureichend beschrieben.

Die vorliegende Untersuchung möchte mit Material, das Tenontosaurus tilletti zugeschrieben werden kann und das im Südosten von Oklahoma gesammelt wurde, die Situation verbessern. Insbesondere ein sehr gut erhaltener Schädel (OMNH 58340) von T. tilletti wurde CT-gescannt und virtuell in seine Einzelkomponenten zerlegt. Diese Elemente wurden hier zusammen mit Rekonstruktionen der internen Weichteil-Zwischenräume wie dem Schädelausguss und cranialen Nervenöffnungen beschrieben und detailliert abgebildet. Diese Beschreibung wird für die Umsetzung einer neuen systematischen Analyse verwendet. Die Untersuchung unterstützt nachdrücklich die Gattung Tenontosaurus, sowie deren Position relativ zu den 'Hypsilophodonten und Iguanodontinen und stimmt weitestgehend mit vorangegangenen Analysen überein.

Schlüsselwörter: Cranial-Anatomie; Beschreibung; Computertomografie (CT); Ornithopode; Iguanodontia; Tenontosaurus

Translator: Eva Gebauer

Arabic

Translator: Ashraf M.T. Elewa

 

 

authorD. Andrew Thomas
Department of Biology
Sam Noble Oklahoma Museum of Natural History
University of Oklahoma
2401 Chautauqua Avenue
Norman, Oklahoma 7307
USA
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Andrew Thomas is a Ph.D. student at the University of Oklahoma, in the town where he was raised. He lives there with his wife and son. Andrew became fascinated with paleontology at an early age on regular field trips to outcrops in Oklahoma, Arkansas, and Texas with his father and brother, collecting the usual marine critters: brachiopods, echinoderms, and gastropods. He never grew out of that early delight in ancient life, and decided to turn that passion into a career in vertebrate paleontology. His research is now focused on the ornithopod dinosaurs of the Jurassic and Cretaceous, especially in the evolutionary trends in basal forms that led to the wildly successful duck-billed hadrosaurs, as well as the ability of ornithopod species of different sizes and shapes to coexist.

 

TABLE 1. Comparisons of non-coded characteristics between the two species of Tenontosaurus from their originally described ranges (T. tilletti from Montana, USA and T. dossi from Texas, USA) and specimens of T. tilletti from the Antlers Formation of Oklahoma. Short descriptors of each characteristic are listed in the first column, and explanations of those characteristics from Tenontosaurus specimens in each of the three known ranges are listed in the second through fourth columns. A short interpretation is included in the fifth column with additional information. Cells colored in blue represent commonalities between one or both of the known Tenontosaurus species with individuals from the Antlers Formation, cells colored in yellow represent differences, and cells colored in red represent unknowns. This table is based off of observations from Ostrom (1970), Forster (1990), and Winkler et al. (1997), as well as personal observations made by the author.