The More the Merrier? A Large Cladistic Analysis of Mysticetes, and Comments on the Transition from Teeth to Baleen

Abstract

The origin of baleen whales, and their specialized mode of filter-feeding, marks an important event in the evolutionary history of mammals that gave rise to one of the most distinctive groups of animals alive today. Recent years have seen the description of a number of important new specimens, as well as the publication of a large number of phylogenetic analyses. Yet, despite this great effort, a broad consensus on even the most fundamental relationships within this group has so far remained elusive, a fact perhaps most strikingly reflected in the ongoing debate regarding the taxonomic placement of the extant gray and pygmy right whales, as well as the question of the relative closeness of relationship of all the extant members of the mysticete crown group. Here, I present the taxonomically most comprehensive phylogenetic analysis of extinct and extant baleen whales carried out to date, based on morphological data and utilizing both maximum parsimony and Bayesian methodologies. The results of this study were well resolved and consistent across methodologies. Apart from recovering a clade comprising the pygmy right whale, gray whales, and rorquals, a grouping new to morphological analyses but supported by a number of molecular studies, this investigation also revealed the former clade to be more closely related to a large number of extinct species than to right whales, thus contradicting previous notions of a closely related mysticete crown group. In addition, this analysis also identified a novel clade comprising nearly all the described archaic toothed mysticetes from the late Oligocene (about 23–28 Ma) to the exclusion of all toothless mysticetes. This finding is consistent with a basic assessment of the functional morphology of toothed mysticete vision, and may have implications for the evolution of mysticete filter-feeding and the recently proposed interpretation of some of these archaic taxa as transitional forms possessing both teeth and baleen at the same time.

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Acknowledgements

This work was supported by The Scottish Association for Marine Science (Research Bursary Z2092/5905/A100), the Nuffield Foundation (Undergraduate Research Bursary URB/35800), and the Bob Savage Memorial Fund of the Department of Earth Sciences, University of Bristol. General support during the later stages of the project was provided by a University of Otago Postgraduate Scholarship. I thank Mike Benton and Ewan Fordyce for their advice and helpful comments on an earlier version of this manuscript, as well as Jonathan Geisler, James Tarver, Graeme Lloyd, Peter Wagner, and Mark Bell for valuable advice and help. Erich Fitzgerald, Eberhard “Dino” Frey, Mette Steeman, Oliver Hampe, Toshiyuki Kimura, and James Westgate generously provided photographs of a number of specimens. David Bohaska and Charles Potter (United States National Museum), Björn Berning (State Museum of Upper Austria), Liliana Póvoas and Álvaro Pinto (Museum of Mineralogy and Geology, Lisbon), Lawrence Barnes, Sam McLeod, Howell Thomas, and Gary Takeuchi (Natural History Museum of Los Angeles County), Oliver Hampe (Natural History Museum of the Humboldt University, Berlin), Eberhard “Dino” Frey (State Museum of Natural History, Karlsruhe), Reinhard Ziegler and Doris Mörike (State Museum of Natural History, Karlsruhe), Mathew Lowe and Ray Symonds (University of Cambridge Zoological Museum), Mihály Gasparik (Hungarian Natural History Museum), Richard Sabin and Jerry Hooker (Natural History Museum, London), Ursula Göhlich (Natural History Museum, Vienna), Peter Howlett (National Museum of Wales), and Rhian Rowson and Andy King (City Museum and Art Gallery, Bristol) kindly provided access to specimens in their care. Most of all, I thank Björn Berning for a warm welcome and his generosity in letting me stay at his house during my visit to Linz, as well as Carl Buell for providing illustrations of various mysticete species.

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Correspondence to Felix G. Marx.

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Supplementary Fig S1
figure6

State frequency distributions of six characters relying on assessments of size of one structure relative to another in the absence of any clear points of reference. Because of the often fragmentary and distorted nature of cetacean fossil material, many of the measurements may be approximations and not entirely accurate, which is why it was decided to use discrete character states, rather than the actual measurements. Measurements were binned into 5% intervals and the final discrete character states delimited by visual inspection. (GIF 98 kb)

ESM 1

(DOC 152 kb)

Data matrix

(TXT 15 kb)

High Resolution Image (EPS 1386 kb)

Appendices

Appendix 1

Institutional Abbreviations

AC—Amgueddfa Cymru (National Museum of Wales, Cardiff); AMP—Ashoro Museum of Paleontology, Ashoro-cho; CMB—City Museum and Art Gallery, Bristol; LACM—Natural History Museum of Los Angeles County; MB—Museum für Naturkunde der Humboldt-Universität zu Berlin (Natural History Museum of the Humboldt University, Berlin); ME—Museum of the Earth, Polish Academy of Sciences, Warsaw; MMG—Museu Mineralógico e Geológico da Universidade de Lisboa (Museum of Mineralogy and Geology, University of Lisbon); MNZ—Museum of New Zealand Te Papa Tongarewa, Wellington; NHM—Natural History Museum, London; NMV—National Museum of Victoria, Melbourne; OL—Oberösterreichisches Landesmuseum (State Museum of Upper Austria, Linz); OM—Museum of Otago, Dunedin; PIN—Paleontological Institute, Moscow; SMNK—Staatliches Museum für Naturkunde, Karlsruhe (State Museum of Natural Sciences, Karlsruhe); SMNS—Staatliches Museum für Naturkunde, Stuttgart (State Museum of Natural History, Stuttgart); UCMP—University of California Museum of Paleontology, Berkeley; UCZM—University of Cambridge Zoological Museum; USNM—United States National Museum, Washington, D.C.

Sources of Data

Outgroup: Zygorhiza kochii, USNM 11962, Kellogg (1936)

Ingroup: Aetiocetus cotylalveus, cast of USNM 25210, Emlong (1966); Aetiocetus polydentatus, cast of AMP 12, Barnes et al. (1995); Aetiocetus weltoni, cast of UCMP 122900, Deméré and Berta (2008); Aglaocetus moreni, Lydekker (1894), Kellogg (1934a); Aglaocetus patulus, USNM 23690, Kellogg (1968d); Archaebalaenoptera castriarquati, Bisconti (2007a); Aulocetus latus, MMG A2, Kellogg (1938–1940); Balaena mysticetus, NHM 1934.10.10.1, SMNS 26400, UCZM C.1.D, C.1.G, USNM 63300, 257513, 258782, Reeves and Leatherwood (1985); Balaena ricei, USNM 22553, Westgate and Whitmore (2002); Balaenella brachyrhynus, Bisconti (2005); Balaenoptera acutorostrata, UCZM C.17.A, C.18.C, USNM 13877, 20931, 61715, Stewart and Leatherwood (1985); Balaenoptera bonaerensis, USNM 504944, Omura (1975), Omura and Kasuya (1976); Balaenoptera borealis, NHM 1888.10.25.1, SMNS 5697, 26401, 26435, UCZM C.16.A, USNM 236680, 504244, 504698, 571340; Balaenoptera edeni, Wada et al. (2003), Yamada et al. (2006); Balaenoptera musculus, NHM 1880.7.28.19, 1882.6.14.1, 1892.3.1.1, 1935.6.24.1, USNM 124326; Balaenoptera omurai, Wada et al. (2003), Yamada et al. (2006); Balaenoptera physalus, UCZM C.13, C.13.L, USNM 16039; Balaenoptera siberi, SMNK (no number), SMNS 47307, Pilleri (1989); Balaenula astensis, Trevisan (1941), Bisconti (2000, 2003); Caperea marginata, MNZ 2061, 2119, NHM 1886.1.27.1, OM A81.2/VT 227, USNM 550146; Cephalotropis nectus, MMG C3, Kellogg (1938–1940); Cetotherium megalophysum, USNM 10593; Cetotherium rathkei, photographs of PIN 1840/1 provided by M. E. Steeman, Brandt (1873), Pilleri (1986); Chonecetus goedertorum, LACM 131146, 138027, Barnes et al. (1995); Cophocetus oregonensis, Packard and Kellogg (1934); Diorocetus chichibuensis, Yoshida et al. (2003); Diorocetus hiatus, USNM 16783, 23494, Kellogg (1968c); Eomysticetus whitmorei, Sanders and Barnes (2002); Eschrichtioides gastaldii, Bisconti (2008); Eschrichtius robustus, NHM 1891.3.3.1, Andrews (1914); Eubalaena glacialis, NHM 1891.9.12.1, USNM 23077, 504886; Eubalaena shinshuensis, Kimura et al. (2007); Herpetocetus transatlanticus, Whitmore and Barnes (2008); Isanacetus laticephalus, Kimura and Ozawa (2002); Janjucetus hunderi, Fitzgerald (2006); Mammalodon colliveri, cast of NMV P199986, Fitzgerald (2010); Mauicetus lophocephalus, MO C62.1, Marples (1956); Megaptera hubachi, MB Ma 28570, Dathe (1983); Megaptera miocaena, USNM 10300, Kellogg (1922); Megaptera novaeangliae, AC Z.1982.058, USNM 13656, 269982, 301636, Winn and Reichley (1985); Metopocetus durinasus, USNM 8518, Kellogg (1968b), Whitmore and Barnes (2008); Metopocetus vandelli, MMG A1, Kellogg (1938–1940); Mixocetus elysius, LACM 882, Kellogg (1934b); Nannocetus eremus, Kellogg (1929), Whitmore and Barnes (2008); Parabalaenoptera baulinensis, Zeigler et al. (1997); Parietobalaena palmeri, USNM 10677, 10688, 16119, Kellogg (1924, 1968e); Parietobalaena yamaokai, Otsuka and Ota (2008); Patriocetus ehrlichii, OL 1999/2, 1999/3ab, Dubrovo and Sanders (2000); Pelocetus calvertensis, USNM 11976, Kellogg (1968a); Physeter catodon, CMB (no number), NHM 1865.7.3.1, Van Beneden and Gervais (1868–1879), Omura et al. (1962); Pinocetus polonicus, photographs of ME VIII/Vm-750 provided by O. Hampe, Czyzewska and Ryziewicz (1976); Piscobalaena nana, SMNK Pal 4050, Bouetel and de Muizon (2006); Protororqualus cuvieri, Van Beneden (1875), Bisconti (2007b); Titanocetus sammariensis, Bisconti (2006); Uranocetus gramensis, Steeman (2009)

Appendix 2

The majority of characters included in the analysis were compiled from A, Kimura and Ozawa (2002); B, Geisler and Sanders (2003); C, Dooley et al. (2004); D, Arnold et al. (2005); E, Bouetel and Muizon (2006); F, Fitzgerald (2006); G, Steeman (2007); H, Bisconti (2008); I, Deméré and Berta (2008); and J, Deméré et al. (2008). The source and original number of each character are indicated in parentheses.

Cranial

  1. 1)

    Length of rostral portion of maxilla: (0) intermediate, rostral portion between 40 and 49% of condylobasal length excluding the premaxillae; (1) short, rostral portion of maxilla <40% of modified condylobasal length; (2) long, rostral portion 50% or larger; (A9, B3, F2)

  2. 2)

    Proximal rostrum: (0) in lateral view, below the level of the supraoccipital and frontal bones; (1) in lateral view, raised to or above the level of the frontal and supraoccipital bones; (H142)

  3. 3)

    Anterior half of maxilla: (0) its lateral edge in cross section forms an angle of more than 45°; (1) flattened maxilla with an angle of less than 45°; (A12, B4, E6, F4, I45, J4)

  4. 4)

    Rostral curvature in lateral view: (0) regular; (1) anterior quarter of rostrum abruptly projects ventrally; (H139)

  5. 5)

    Lateral border of maxilla anterior to lateral process: (0) concave; (1) straight; (2) continuously convex; (3) divided into a short posterior part subparallel to the sagittal plane and a longer straight anterior part converging on the tip of the rostrum; (H107)

  6. 6)

    Width of rostrum at antorbital notch (base of rostrum): (0) fairly wide, between 40 and 54% of the bizygomatic width; (1) narrow, <40% of the bizygomatic width; (2) wide, rostral width equal to or >55% of the bizygomatic width; (B7, F7, H67, I40)

  7. 7)

    Premaxilla in dorsal view; (0) portion anterior to nasal opening narrows or remains the same width anteriorly; (1) widens at anterior end; (B8, F8, H106)

  8. 8)

    Premaxillae adjacent to anterolateral corner of nasal, skull in lateral view: (0) stay the same width as more anteriorly on rostrum or become thinner dorsoventrally; (1) widen dorsoventrally; (E2, G14)

  9. 9)

    Premaxillae adjacent to and at posterior edge of nasal opening: (0) do not clearly overhang maxillae; (1) overhang maxillae; (A17, B110, F100, H128)

  10. 10)

    Posterior region of rostral edge: (0) lateral margin is straight or gently concave with skull in dorsal view; (1) bowed outward causing a V- or U-shaped antorbital notch; (B11, F12, J78)

  11. 11)

    Steep face on anterolateral edge of zygomatic process of maxilla clearly separating it from rostral portion of maxilla: (0) absent; (1) present; (B13, E9, F14, H7, I39)

  12. 12)

    Anterior border of zygomatic process of maxilla and anterior border of supraorbital process of frontal in dorsal view: (0) maxilla closely approximates or underlies frontal; (1) separated by a basin (note: not the space for the reception of the lacrimal);

  13. 13)

    Distinct pocket between ascending process of maxilla dorsally and supraorbital process of frontal ventrally; (0) absent; (1) present; (J17)

  14. 14)

    Posterior portions of maxillae: (0) situated lateral to frontals; (1) situated lateral to nasals; (2) situated lateral to both nasals and premaxillae; (A15, I46, J13)

  15. 15)

    Posterior end of ascending process of maxilla: (0) lateral edges convergent, process tapers to a point; (1) lateral edges parallel; (2) lateral edges divergent, posterior process transversely expanded at posterior end; (B14, E12, F15, G6, J18)

  16. 16)

    Antorbital notch formed by maxilla: (0) absent; (1) present; (A11, E8, G16, H80)

  17. 17)

    Anterior border of zygomatic process of maxilla projecting anteriorly beyond antorbital notch; (0) absent; (1) present;

  18. 18)

    Palatal surface of rostrum: (0) flat or gently concave; (1) bears pronounced longitudinal keel (formed by vomer and medial edges of maxillae) along the midline of the rostrum; (B16, E5, F17, G23, H25, I41, J36)

  19. 19)

    Palatal window exposing vomer: (0) absent; (1) present; (I13, J96)

  20. 20)

    Palatal nutrient foramina and sulci: (0) absent; (1) present; (B17, E4, F18, G2, I16, J38)

  21. 21)

    Palatine/maxilla suture in ventral view: (0) suture between both palatines and both maxillae is straight transversely or bowed anteriorly; (1) maxillae have posterior processes that separate palatines anteriorly, suture around midline is V-shaped and points posteriorly; (B20, F21, J40)

  22. 22)

    Anterior edge of narial fossa: (0) located in posterior three-quarters of rostrum; (1) located in anterior quarter of rostrum;

  23. 23)

    Rostrum in lateral view: (0) rostrum has a distinct step-like profile, the portion anterior to the nasals being abruptly depressed; (1) transition from the anterior end of the rostrum to the nasals is smooth; (E2, G14)

  24. 24)

    Rostrum shape: (0) narrow, width at antorbital notches <80% the length of the rostrum, as measured from its tip to the antorbital notches; (1) broad, width at antorbital notches >80% the length of the rostrum;

  25. 25)

    Teeth in adult individuals: (0) present; (1) absent; (G1, H15, I42, J61)

  26. 26)

    Skull length about one-third total body length: (0) absent, skull shorter; (1) present; (H56)

  27. 27)

    Diameter of orbit, as measured between distalmost points on orbital rims of pre- and postorbital processes: (0) less than 25% of bizygomatic width; (1) 25% or more;

  28. 28)

    Anterior edge of supraorbital process of frontal: (0) transverse line lateral to ascending process of the maxilla; (1) anteriorly directed line lateral to the ascending process of the maxilla (lateralmost point of line is anterior); (2) posteriorly directed line lateral to the ascending process of the maxilla (medialmost point of line is anterior); (3) tapers to a point lateral to ascending process of maxilla; (A13, B49, E25, F50, G9, H110)

  29. 29)

    Transverse length of anterior edge of supraorbital process of frontal lateral to ascending process of maxilla: (0) longer than the combined transverse length of the adjacent rostral bones (maxilla, premaxilla, nasal), as measured from the lateralmost point of the ascending process of the maxillae to the sagittal plane; (1) shorter than the combined transverse length of the adjacent rostral bones;

  30. 30)

    Posterior border of supraorbital process of frontal: (0) concave; (1) straight; (B60, E29, F61)

  31. 31)

    Supraorbital processes of frontal; (0) horizontal; (1) gradually slope lateroventrally away from vertex of skull; (2) abruptly depressed at base to a level noticeably below that of dorsal surface of interorbital region; (A3, B46, C29, E28, F47, G11, H24, I31, J23)

  32. 32)

    Anterior border of supraorbital process of frontal lateral to ascending process of maxilla, skull in dorsal view: (0) bordered by lacrimal and maxilla; (1) bordered by lacrimal only;

  33. 33)

    Shape of supraorbital process of frontal in dorsal view: (0) medial portion as long (anteroposteriorly) as lateral; (1) medial portion distinctly shorter than lateral, supraorbital process has a triangular outline; (2) medial portion longer than lateral; (E26)

  34. 34)

    Anteroposterior length of supraorbital process of frontal: (0) roughly as long (at the dorsal edge of the orbit) as wide transversely or longer; (1) wider than long (up to twice the length); (2) distinctly wider than long (more than twice its length above the orbit); (A6, E27, G10, I2, J22)

  35. 35)

    Shape of dorsal edge of orbit in dorsal view: (0) roughly straight or slightly concave; (1) deeply notched in relation to total transverse width of process; (A5, E34, I6)

  36. 36)

    Position of line joining anteriormost points of supraorbital processes of frontals: (0) passing through the nasals length; (1) posterior or on the same level as the posterior extremity of the nasals; (2) on the same level as the anterior extremity of the nasals; (3) anterior to the anterior extremity of the nasals; (B80, E23, F83, G4, H112, J6)

  37. 37)

    Dorsal edge of orbit relative to lateral edge of rostrum, skull in lateral view: (0) orbit elevated above the level of the edge of the rostrum; (1) orbit low, in line with edge of rostrum or slightly above it; (2) below the level of the edge of rostrum; (B47, E33, F48)

  38. 38)

    Lacrimal in dorsal view: (0) situated entirely lateral to the ascending process of the maxilla; (1) lacrimal extends medially and separates the lateral corner of the ascending process from the more anterior portion of the maxilla; (B50, F51, H165, I12, J19)

  39. 39)

    Maxillary infraorbital plate; (0) absent; (1) present; (B59, E7, F60, H6, I29, J16)

  40. 40)

    Maxillary window originating from posterior border of infraorbital plate: (0) absent; (1) present; (J37)

  41. 41)

    Anteromedial corner of supraorbital process of frontal extending to a point medial to antorbital notch: (0) absent; (1) present;

  42. 42)

    Angle between posterior margin of zygomatic process of maxilla and lateral margin of ascending process of maxilla: (0) larger than 90°; (1) 90° or smaller;

  43. 43)

    Premaxillary foramina: (0) absent; (1) present; (A16, B69, F71)

  44. 44)

    Maxilla/frontal suture: (0) maxilla overrides anteromedial corner of supraorbital process of frontal; (1) maxilla almost completely overrides frontal; (A1, B76, C37, F78, I3, J17)

  45. 45)

    Maxilla, geometry/arrangement of lateral nutrient foramina and associated sulci: (0) posterior foramina with sulci radially arranged (no open maxillary groove) and anterior foramina with elongate sulci parasagittally arranged; (1) posterior foramina coincident with open maxillary groove with numerous short transverse sulci and anterior foramina with elongate sulci parasagittally arranged; (2) posterior foramina single without well-developed sulci and anterior foramina with elongate sulci parasagittally arranged; (3) posterior foramina multiple (roughly in two rows) without well-developed sulci and anterior foramina with elongate sulci parasagittally arranged; (J54)

  46. 46)

    Posteriormost edge of ascending process of maxilla: (0) in transverse line with anterior half of supraorbital process of frontal or in line with halfway point, anteroposteriorly, of supraorbital process; (1) in line with posterior half of supraorbital process up to the postorbital process, or in line with postorbital process of frontal; (2) extends behind the postorbital process of the frontal; (3) situated well anterior to anterior edge of orbit; (B77, F79, H73, I7, J15)

  47. 47)

    Posteriormost edge of ascending process of maxilla situated posterior to anteriormost point of orbitotemporal crest: (0) absent; (1) present;

  48. 48)

    Medial contact of ascending processes of maxillae: (0) contact absent, processes widely separated; (1) processes contacting at their tips or very nearly so; (E13)

  49. 49)

    Posterior extension of premaxillae relative to posterior extension of maxillae: (0) anterior; (1) at the same level or posterior; (E18)

  50. 50)

    Posterior border of ascending process of maxilla: (0) transversely oriented or medial corner more posterior; (1) lateral corner more posteriorly situated;

  51. 51)

    Posterior border of ascending process of maxilla: (0) pointed or rounded; (1) squared off; (B14, E12, F15, G6, H81, J18)

  52. 52)

    Relationship between rostral and cranial bones, skull in lateral view: (0) smooth or angular transition; (1) the two sets of bones form a distinct apex; (H140)

  53. 53)

    Position of inflection of premaxilla, skull in dorsal view: (0) in line with posterior half of rostrum; (1) in line with anterior edge or anterior half of supraorbital process of frontal; (2) in line with posterior half of supraorbital process up to the postorbital process, or in line with postorbital process of frontal; (B108, F98)

  54. 54)

    Nasal, length relative to bizygomatic width: (0) long (40% or more of bizygomatic width); (1) short (<40% of bizygomatic width); (J7)

  55. 55)

    Position of posteriormost edge of nasals: (0) in transverse line with anterior half of supraorbital process of frontal or in line with the halfway point, anteroposteriorly, of supraorbital process; (1) in line with posterior half of supraorbital process up to the postorbital process, or in line with postorbital process of frontal; (2) located posterior to postorbital process; (3) just anterior to or in a transverse line with anterior edge of supraorbital process of frontal; (A26, B122, F112, H111, I28, J12)

  56. 56)

    Orbitotemporal crest: (0) positioned along posterior border of supraorbital process of frontal; (1) positioned on dorsal surface of supraorbital process; (B131, E24, F121, H19, I43, J79)

  57. 57)

    Development of orbitotemporal crest: (0) mainly straight; (1) distal half abruptly projecting posterolaterally; (H151)

  58. 58)

    Shape of temporal fossa: (0) longer (anteroposteriorly) than wide (lateromedially), or as wide as long; (1) wider than long; (E32, G12)

  59. 59)

    Intertemporal constriction: (0) longer anteroposteriorly than wide transversely, medial edges of temporal fossae are straight; (1) longer anteroposteriorly than wide transversely, medial edges of temporal fossae are concave; (2) wider transversely than long anteroposteriorly; (I8)

  60. 60)

    Ascending process of maxilla on dorsal surface of skull: (0) posteriormost point anterior to anteriormost point of supraoccipital; (1) posteriormost point is posterior to anteriormost point of supraoccipital; (B129, F119)

  61. 61)

    Parietal and interparietal, if present: (0) anteriormost point behind supraorbital process of frontal, or in line with postorbital process; (1) anteriormost point in line with supraorbital process; (H22, I4, J95)

  62. 62)

    Parietals in dorsal view: (0) contact each other on the midline or are separated by an interparietal; (1) are in place in the skull roof but are visible only as small triangular areas at edges of the intertemporal constriction, supraoccipital overlaps most of the median portions of the parietals and obscures them; (2) are completely absent in the skull roof; (B134, E35, F124, H34, J25)

  63. 63)

    Anteriormost point of parietal and interparietal, if present: (0) more posterior than, or in line with posterior border of ascending process of the maxilla; (1) more anterior; (A28, B133, F123, H163)

  64. 64)

    Anteriormost point of supraoccipital, in dorsal view: (0) in transverse line with space between posterior edge of skull (condyles or exoccipitals, whichever is more posterior) and the posteriormost point of the subtemporal crest/medial base of the zygomatic process of the squamosal; (1) in line with gap between postorbital process and the posteriormost point of the subtemporal crest/medial base of the zygomatic process of the squamosal, or in line with the latter; (2) in line with posterior half of supraorbital process of frontal up to the postorbital process, or in line with postorbital process of frontal; (3) in line with anterior half of supraorbital process of frontal or halfway point, anteroposteriorly, of supraorbital process; (4) located just anterior to or in a transverse line with anterior edge of supraorbital process of frontal; (A2, B139, E39, F129, G5, H78, J27)

  65. 65)

    Position of posterior apex of nuchal crest: (0) anterior to or in line with the posteriormost point of the occipital condyles; (1) posterior to the condyles; (H83)

  66. 66)

    Contacts of alisphenoid in temporal fossa: (0) alisphenoid located between frontal, squamosal, parietal, palatine, and pterygoid; (1) alisphenoid located between frontal, squamosal, parietal, and pterygoid, but not palatine; (2) alisphenoid located between squamosal, parietal, and pterygoid, but not palatine and frontal; (3) alisphenoid located between parietal and pterygoid, but not palatine, frontal, and squamosal; (4) no alisphenoid exposed in temporal fossa; (H113)

  67. 67)

    Zygomatic process of squamosal: (0) directed anteromedially; (1) directed anteriorly; (2) directed anterolaterally; (B142, E42, F132, H91, J30)

  68. 68)

    Zygomatic process of squamosal in lateral view: (0) dorsal and ventral borders parallel or convergent; (1) process is expanded dorsoventrally both anteriorly and posteriorly, with a medial constriction; (I10)

  69. 69)

    Anterior tip of zygomatic process of squamosal: (0) does not contact postorbital process of frontal, anteriormost point of zygomatic process is situated entirely behind the postorbital process; (1) does not contact postorbital process, anteriormost point of zygomatic process is situated lateral to postorbital process; (2) anteriormost point of zygomatic process contacts or is situated below the postorbital process; (A21, E31, H93, I11, J21)

  70. 70)

    Supramastoid crest of zygomatic process: (0) present; (1) absent; (E43, H158)

  71. 71)

    Axis of main squamosal development: (0) anteroposterior; (1) dorsoventral; (A19, H35, J33)

  72. 72)

    Transverse width of squamosal lateral to exoccipital, skull in posterior view: (0) intermediate width, width between 10 and 34% the distance between sagittal plane and lateral edge of exoccipital; (1) wide, width between 35 and 49% of that distance; (2) very wide, width 50% or more of that distance; (3) narrow, exposed portion of squamosal <10% of that distance; (B145, F135, J34)

  73. 73)

    Orientation of postglenoid process in lateral view: (0) subvertical to anteriorly projecting; (1) subvertical to posteriorly projecting; (E45)

  74. 74)

    Orientation of postglenoid process in posterior view: (0) ventrally oriented; (1) ventrolaterally oriented; (E46)

  75. 75)

    Squamosal cleft: (0) absent; (1) present; (H69, J32)

  76. 76)

    Paired tubercles on supraoccipital shield: (0) absent; (1) present;

  77. 77)

    Lateral edges of supraoccipital in dorsal view: (0) convex; (1) straight or concave; (H62, J29)

  78. 78)

    Twisting of postglenoid process in ventral view: (0) not twisted and roughly transverse to the sagittal axis of the skull; (1) twisted clockwise on the left side and anticlockwise on the right side; (E47)

  79. 79)

    Pterygoids in ventral view: (0) exposed for their entire or most of their entire length; (1) anterior half covered by palatines; (2) pterygoids are almost entirely covered by palatines; (A18, G22, H46, I15, J39)

  80. 80)

    Position of foramen ‘pseudo-ovale’: (0) absent; (1) foramen lies within pterygoid; (2) foramen located between squamosal and pterygoid; (3) foramen lies within squamosal, contact with pterygoid (when present) by a suture; (4) foramen located between squamosal and pterygoid, but with an incomplete outer edge; (H11, H117, J35)

  81. 81)

    Basioccipital crest: (0) narrow transversely; (1) wide and bulbous; (B191, E51, F181, H8, J42)

  82. 82)

    Angle formed by basioccipital crests in ventral view: (0) diverging posteriorly; (1) parallel or subparallel with no angle formed; (B194, F184, I18)

  83. 83)

    Paroccipital process, skull in dorsal view: (0) extends anterior to the posterior edge of occipital condyle; (1) level with or posterior to posterior edge of condyle; (A29, B197, E55, F187, J43)

Periotic

  1. 84)

    Elongation of pars cochlearis towards cranial cavity, dorsally and medially: (0) absent; (1) present, anteroposterior width at base shorter than proximodistal length (A61, B230, C12, E77, F220, G38, H75, J46)

  2. 85)

    Articulation of anterior process of periotic and tympanic bulla: (0) little or no contact, or contact present with fovea epitubaria on the anterior process of the periotic; (1) fused forming a ridge-like pedestal; (A53, B255, C3, C6, F245, H29)

  3. 86)

    Lateral projection of anterior process of periotic: (0) absent or blunt projection on anterior process; (1) long, blade-like projection half the length of the anterior process or longer; (A54, B211, C4, E69, F201, G28, H55, J47)

  4. 87)

    Hiatus epitympanicus: (0) present; (1) absent or indistinct; (A57, C8)

  5. 88)

    Proximal opening of facial canal, internal acoustic meatus (sensu Mead and Fordyce but excluding proximal opening of facial canal) and aperture for cochlear aqueduct dorsally on pars cochlearis are aligned: (0) absent; (1) present; (G39)

  6. 89)

    Aperture for cochlear aqueduct: (0) smaller than aperture for vestibular aqueduct; (1) approximately the same size; (B227, F217)

  7. 90)

    Morphology of proximal opening of facial canal: (0) roughly circular or circular and continuous with a broad (not fissure-like) hiatus Fallopii; (1) continuous with a fissure-like hiatus Fallopii; (A69, B238, C20, E75, F228, J52)

  8. 91)

    Articulation surfaces on posterior processes of tympanic and periotic; (0) unfused; (1) fused in adults; (A76, B241, C27, E62, F231, G37, H28)

  9. 92)

    Facial sulcus distal to stylomastoid notch: (0) short, no sulcus posterior to stylomastoid notch; (1) long but relatively shallow sulcus on posterior process of periotic or the compound periotic-tympanic posterior process, sulcus gradually disappears distally; (2) long and deep sulcus along the entire length of the posterior process of periotic or the compound periotic-tympanic posterior process; (A75, B244, C26, E83, F234, H105)

  10. 93)

    Morphology and exposure of compound posterior process of periotic and tympanic (whether fused or not): (0) short, processes not or barely exposed on the lateral wall of the skull; (1) processes exposed laterally and conical to tetrahedral, strongly widening distally; (2) processes exposed and cylindrical or flattened; (A77, B249, C28, E85, F239)

  11. 94)

    Neck of posterior process of periotic: (0) transversely constricted; (1) transversely and dorsoventrally constricted; (2) absent; (A73, B247, C24, F237, G36)

Tympanic Bulla

  1. 95)

    Orientation of main axes of tympanic bullae as viewed in situ, skull in ventral view: (0) parallel; (1) diverging posteriorly; (2) diverging anteriorly; (E56)

  2. 96)

    Orientation of outer lip of tympanic bulla: (0) faces laterally; (1) faces ventrolaterally to ventrally; (E61)

  3. 97)

    Ventral margin of sigmoid process: (0) present, either as distinct margin or as posterior margin of the sigmoid process projecting anteriorly to a point ventral or anterior to the tip of the sigmoid process; (1) absent; in its place the lateral margin of sigmoid process smoothly turns into a nearly vertical sulcus on the lateral side of the bulla; (B259, F249, G45)

  4. 98)

    Elliptical foramen of tympanic bulla: (0) present as a distinct foramen, so that connection between tympanic bulla and its posterior process is split into two pedicles; (1) outer posterior pedicle of bulla is lost, foramen is open laterally; (B261, F251)

  5. 99)

    Shape of elliptical foramen of tympanic bulla: (0) deep, the foramen incises into the wall of the bulla below the level of the base of the conical process; (1) shallow, the foramen does not incise into the wall of the bulla below the level of the base of the conical process; (G44)

  6. 100)

    Medial/dorsal lobe of tympanic bulla: (0) present as a distinct lobe extending to the posterior edge of the bulla and separated from the ventral lobe by a deep median furrow (posterior face of bulla bears interprominental notch); (1) present as an eminence on the involucrum anterior to posterior edge of bulla or absent; (B269, E58, F259)

  7. 101)

    Eustachian outlet, tympanic bulla in anterior view: (0) marked groove, ventralmost point of outlet is depressed below the level of the involucrum; (1) ventral border of outlet is an almost horizontal rim at or close to the level of the involucrum;

  8. 102)

    Sigmoid process, lateral view: (0) overlaps anterior half or more of the conical process; (1) no or only slight overlap, conical process is well separated from posterior edge of sigmoid process;

  9. 103)

    Ridge on inside of tympanic bulla: (0) present, transverse ridge extends laterally from involucrum and partially divides cavum tympani into anterior and posterior portions; (1) absent; (B272, F262, H154)

  10. 104)

    Ventral side of tympanic bulla: (0) transversely concave; (1) flat or convex;

Mandible

  1. 105)

    Medial surface of middle part of mandible: (0) flat or convex, similar to the lateral surface of the mandible; (1) distinctly flattened with respect to the lateral surface of the mandible; (A42, E91)

  2. 106)

    Mandibular symphysis: (0) sutured or fused; (1) not sutured; (A33, B40, E88, F41, H9, I26, J53)

  3. 107)

    Mandible in life position in lateral view: (0) straight; (1) arched dorsally; (A36, B38, C34, E90, F39)

  4. 108)

    Neck of mandible and condyle: (0) forms part of the curvature of the horizontal ramus of the mandible; (1) reflexed, giving the jaw a distinctly sinusoidal outline in dorsal view; (J55)

  5. 109)

    Horizontal ramus of mandible in dorsal view: (0) bowed medially; (1) straight or slightly bowed laterally, a line drawn from the posteriormost to anteriormost points stays within the body of the mandible; (2) strongly bowed outward, line from anterior to posterior points does not entirely lie within the body of the mandible; (A37, B42, E87, F43, G55, H21, I25, J57)

  6. 110)

    Anterior extremity of mandible relative to medial portion of horizontal ramus: (0) vertical; (1) twisted with the ventral edge shifted medially; (2) apex of the mandible shifted to an almost horizontal position; (A39, E89, G60, H50, J89)

  7. 111)

    Mandible in lateral view: (0) constant height; (1) constricted medially in a dorsoventral direction; (2) increasing in height anteroposteriorly; (A43, E90, H95)

  8. 112)

    Mandibular foramen: (0) dorsoventral height approximately that of mandible; (1) dorsoventral height about half that of mandible or less; (A38, G58, H159, J58)

  9. 113)

    Anterior border of mandibular foramen: (0) round; (1) triangular; (H160)

  10. 114)

    Satellite process (sensu Bisconti and Varola 2006): (0) absent; (1) present;

  11. 115)

    Mandible, relative position of anterior border of mandibular foramen: (0) anterior to tip of coronoid process; (1) in line with tip or posterior edge of coronoid process; (2) posterior to coronoid process; (E97, G58, J87)

  12. 116)

    Subcondylar furrow: (0) absent; (1) present medially only; (2) deep groove on the posterior surface separating the condyle and angular process medially and laterally; (E96, G59, J86)

  13. 117)

    Coronoid process: (0) anterior border convex and merging back into a horizontal dorsal border, posterior border roughly vertical, anteroposterior length at base greater than maximum dorsoventral height; (1) anterior and posterior border roughly parallel, process points backward and overhangs the mandibular neck; anteroposterior length at base shorter than maximum dorsoventral height; (2) anterior and posterior borders are convergent, process is triangular; (I27)

  14. 118)

    Mandible, postcoronoid elevation: (0) absent; (1) present; (J82)

  15. 119)

    Articular surface of mandibular condyle: (0) posterodorsal or posterior; (1) articular surface is directed dorsally, neck and angular process of mandible not elevated above the ventral border of horizontal ramus of mandible; (2) articular surface is directed dorsally, neck and angular process of mandible are elevated above the ventral border of horizontal ramus of mandible and directed posterodorsally; (A35, E99, H38, J59)

  16. 120)

    Gingival foramen on mandible: (0) absent; (1) present; (G61)

  17. 121)

    Sulcus for attachment of mylohyoid muscle on ventromedial surface of mandible: (0) absent; (1) present; (H49, J56)

Postcranial

  1. 122)

    Transverse process of atlas at base less than or roughly equal to half height of articular surface: (0) absent; (1) present; (G63)

  2. 123)

    Foramen transversarium in axis: (0) present; (1) absent; (H61)

  3. 124)

    Cervical vertebrae: (0) separate; (1) partly fused; (2) fused; (A45, B278, B279, C36, G62, H48, J63)

  4. 125)

    Sternum: (0) composed of several bones; (1) composed of one bone; (B290, H13, J90)

  5. 126)

    Sternum: (0) several ribs attach to sternum; (1) one rib attaches to sternum; (B291, H14, J90)

  6. 127)

    Coracoid process of scapula: (0) present; (1) absent; (A48, B292, H97, J65)

  7. 128)

    Acromion process of scapula: (0) present; (1) absent; (H98, J64)

  8. 129)

    Humerus: (0) longer than radius and ulna; (1) same length; (2) shorter than radius and ulna; (A50, B297, C40, H96, J66)

  9. 130)

    Olecranon process: (0) present as a distinct process; (1) absent; (B298)

  10. 131)

    Manus: (0) pentadactyl; (1) tetradactyl; (A49, B299, C35, H70, J67)

Soft Tissue

  1. 132)

    Ventral throat grooves: (0) absent or few (2–10) confined to throat region; (1) numerous and terminate midbody; (2) numerous and extend to or posterior to the umbilicus; (B301, H52, J69)

  2. 133)

    Ventral throat pouch: (0) absent; (1) present; (J70)

  3. 134)

    Tongue: (0) muscular; (1) reduced and predominantly connective tissue; (J75)

  4. 135)

    Temporomandibular joint: (0) synovial; (1) non-synovial, fibrocartilagenous mass originates in the glenoid fossa and envelopes the mandibular condyle;

  5. 136)

    Longitudinal ridges on rostrum: (0) absent or indistinct; (1) single median ridge; (2) three longitudinal ridges; (J76)

  6. 137)

    Dorsal fin: (0) present as fin or dorsal hump; (1) absent; (B304, H51, J68)

  7. 138)

    Baleen: (0) absent; (1) present; (A30, B1, F1, H17, J71)

Color Patterns

  1. 139)

    Rostral saddle: (0) absent; (1) present; (2) well developed; (D1)

  2. 140)

    Blowhole streaks: (0) absent; (1) present; (2) well developed; (D2)

  3. 141)

    Dark nape field: (0) absent; (1) dark nape field present; (2) nape field light; (D3)

  4. 142)

    Form of dorsal portion of nape streak: (0) nape streak absent; (1) V-shaped chevron; (2) nape blaze linear to diffuse; (D4)

  5. 143)

    Ventral nape streak: (0) absent; (1) present; (D5)

  6. 144)

    Ear stripe: (0) absent; (1) present; (D6)

  7. 145)

    Basal flipper coloration: (0) uniformly colored flipper; (1) generally uniform but with white leading edge; (2) white; (3) dark; (D7)

  8. 146)

    Distal flipper coloration: (0) uniformly colored flipper; (1) generally uniform but with a light leading edge; (2) dark grey; (D8)

  9. 147)

    Axillary patch: (0) absent; (1) present; (2) well developed; (D9)

  10. 148)

    Thorax field: (0) body uniformly colored; (1) body shows two tone pigment with darker back and lighter underside, with no indications of an intermediate light gray pigment field; (2) light gray transitional lateral field present; (3) thorax field and flank patch present; (D10)

  11. 149)

    Caudal chevron: (0) absent; (1) single chevron; (2) double chevron; (D11)

  12. 150)

    Asymmetry: (0) absent; (1) present but subtle; (2) well developed; (D13)

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Marx, F.G. The More the Merrier? A Large Cladistic Analysis of Mysticetes, and Comments on the Transition from Teeth to Baleen. J Mammal Evol 18, 77–100 (2011). https://doi.org/10.1007/s10914-010-9148-4

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Keywords

  • Cetacea
  • Mysticeti
  • Baleen whale
  • Evolution
  • Phylogeny
  • Cladistic
  • Bayesian