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A New Species of Neurankylus from the Milk River Formation (Cretaceous: Santonian) of Alberta, Canada, and a Revision of the Type Species N. eximius

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Morphology and Evolution of Turtles

Part of the book series: Vertebrate Paleobiology and Paleoanthropology ((VERT))

Abstract

A new species of Neurankylus (N. lithographicus sp. nov.) is described on the basis of skull and shell material from the Santonian-aged Milk River Formation, Alberta, Canada. The genus Neurankylus is also rediagnosed on the basis of the Milk River material and on new material pertaining to the type species N. eximius. N. eximius previously was considered to be a long-lived and cosmopolitan taxon. New Neurankylus material provides insights into the range of morphological variation present in the genus and indicates that many specimens previously referred to N. eximius may belong to different species. The congeners recognized in this chapter have a more restricted geographical and temporal range than has been suggested previously. A new phylogenetic analysis of all known baenid taxa, including all described species of Neurankylus and several basal paracryptodiran taxa of uncertain affinities, yields two important results: a monophyletic Neurankylus is recovered as a basal radiation within Baenidae and parallel evolution is identified among many features previously regarded as synapomorphies for Baenidae. In light of this study and other recent work on turtle systematics, it is now apparent the biogeography and biostratigraphy of Cretaceous turtles may have been more complex than previously appreciated.

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Acknowledgments

We thank D. Brinkman, P. Currie, M. Wilson, T. Lyson, and the entire UALVP for helpful discussion, resources, and guidance, as well as T. Lyson and W. Joyce for providing the character-taxon matrix for the phylogenetic analysis. Financial support for this research was provided by the Jurassic Foundation and the University of Alberta, Department of Biological Sciences (to DWL), Alberta Ingenuity, National Science Foundation, and Yale Institute for Biospheric Studies (to NRL), National Sciences and Engineering Research Council of Canada Graduate Scholarship and Discovery Grant (to DCE). Specimens were expertly prepared by I. Morrison, J. McCabe, and D. Lloyd. We are grateful to R. Audet for land access permission, the Royal Tyrrell Museum of Palaeontology and the Sloboda family for logistical support, B. Strilisky and T. Lyson for access to specimens, and the 2007 Southern Alberta Dinosaur Research Group field crew for their hard work. This manuscript represents part of DWL’s MSc thesis at the University of Alberta. An earlier version of this manuscript was greatly improved by P. Currie, D. Brinkman, M. Wilson, A. Wolfe, and M. Burns. Reviewers R. Sullivan and T. Lyson and editors D. Brinkman and J. Gardner provided excellent constructive criticism for the improvement of this manuscript. Lastly, we salute Eugene Gaffney for his contributions to baenid research, without which the current study would not have been possible.

Author information

Authors and Affiliations

  1. University of Alberta Laboratory for Vertebrate Paleontology, University of Alberta, CW 405 Biological Sciences Building, Edmonton, AB, T6G 2E9, Canada

    Derek W. Larson

  2. Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT, 06520-8109, USA

    Nicholas R. Longrich

  3. Department of Natural History (Palaeobiology), Royal Ontario Museum, 100 Queen’s Park, Toronto, ON, M5S 2C6, Canada

    David C. Evans

  4. Cleveland Museum of Natural History, 1 Wade Oval Drive, University Circle, Cleveland, OH, 44106, USA

    Michael J. Ryan

Authors
  1. Derek W. Larson
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  2. Nicholas R. Longrich
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  3. David C. Evans
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  4. Michael J. Ryan
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Corresponding author

Correspondence to Derek W. Larson .

Editor information

Editors and Affiliations

  1. Royal Tyrell Museum, Drumheller, Alberta, Canada

    Donald B. Brinkman

  2. Museum of Paleontology, University of California, Berkeley, California, USA

    Patricia A. Holroyd

  3. Royal Tyrrell Museum, Drumheller, Canada

    James D. Gardner

Appendices

Appendices

Appendix 1

Modifications to character matrix of Lyson and Joyce (2009b).

(a) Taxa added (see Appendix 2 for list of specimens and sources):

Dinochelys whitei; Dorsetochelys delairi; “Dorsetochelys” buzzops; Uluops uluops; Arundelemys dardeni; Thescelus insiliens; Neurankylus baueri; Neurankylus ROM 864; Neurankylus lithographicus; Neurankylus wyomingensis; and Lance Formation Neurankylus.

(b) Modified characters:

Character 36: rescored for Neurankylus eximius

Character 38: changed and combined with Character 57.

Character 39: scored for Peckemys brinkman.

Character 50: rescored for consistency.

Character 53: scored for Peckemys brinkman.

Character 57: deleted, because combined with Character 38.

Character 60: deleted, because too variable to be reliable.

(c) New characters:

Character 71. Temporal emargination: 0) does not expose otic cap-sule; (1) stapedial foramen exposed in dorsal view; (2) anterior to an-terior margin of otic capsule.

Character 72. Contribution of supraoccipital to stapedial foramen: (0) enters stapedial foramen; (1) excluded from stapedial foramen.

Character 73. Anterior nuchal projection: (0) absent; (1) present.

Character 74. Skull ornamentation: (0) pustolose (Glyptops-like); (1) rugose.

Character 75. Foramen posterius canalis caroticum internus position: (0) in posterior half; (1) in anterior half of pterygoid–basisphenoid suture.

Character 76. Ventral angle between pterygoid occipital process and transverse process of pterygoid: (0) less than 90°; (1) more than 90° or equal.

Character 77. Narrowest part of ventral pterygoid: (0) even or posterior to anteriormost portion of ventral exposure of basisphenoid; (1) anterior to basisphenoid.

Character 78. Opisthotic in posterior view: (0) width less than 1.5 times height; (1) width greater than 1.5 times height.

Character 79. External ventrolateral quadrate-quadratojugal suture: (0) shorter; (1) roughly equal in height or taller than tympanic recess.

Character 80. Foramen nervi hypoglossi directed: (0) posterolaterally not visible from posterior view; (1) posteriorly visible from posterior view.

Character 81. Exoccipital processes of basioccipital: (0) thinner; (1) roughly same thickness as height of condyle.

Character 82. Anterior border of frontals: (0) extends anterior to prefrontals; (1) does not extend past prefrontals.

Character 83. Anterior border of frontals: (0) pointed anteromedially; (1) straight.

Character 84. Shell ornamentation: (0) rugose (Glyptops-like); (1) faintly ridged.

Character 85. Dorsal medial keel on posterior vertebrals: (0) absent; (1) present.

Character 86. Dorsolateral gutters on carapace: (0) absent; (1) present.

Character 87. Cervical scute: (0) small and rectangular long edge on carapace margin; (1) small and rectangular short edge on margin; (2) not as above.

Character 88. Anterior edge of nuchal: (0) slightly recessed; (1) anterior or even with first marginals.

Character 89. Nuchal lateral margins: (0) tapers anteriorly; (1) parallel; (2) widens anteriorly.

Character 90. Second and third vertebrals: (0) do not narrow anteriorly; (1) narrow anteriorly.

Character 91. Fifth vertebral: (0) wide anterolateral sulci not present on second suprapygal (same width as fourth vertebral); (1) narrow sulci present on second suprapygal (narrower than fourth vertebral).

Character 92. Fourth marginal resembling asymmetrical trapezoid: (0) no; (1) yes, widest part posterior.

Character 93. Early fusion of first suprapygal to eighth neural: (0) absent; (1) present.

Character 94. Posterior neurals: (0) hexagonal; (1) square.

Character 95. First–second costal suture: (0) slightly posteriorly inclined or perpendicular to long axis; (1) slightly anteriorly inclined; (2) greatly anteriorly inclined.

Character 96. Greatest plastron length: (0) less; (1) equal or greater than greatest carapace width.

Character 97. Carapace width to carapace length: (0) around 0.8; (1) around 0.85.

Character 98. Plastron length to carapace length: (0) less than or equal 0.8; (1) greater than 0.8.

Character 99. Anterior lobe length to posterior lobe length: (0) 0.82 or less; (1) greater than 0.84.

Character 100. Intergular shape: (0) rectangular with large intergular humeral sulcus; (1) heart-shaped with little or no intergular-humeral sulcus; (2) semicircular, no humeral contact.

Character 101. Intergulars: (0) do not overlap entoplastron; (1) overlap entoplastron.

Character 102. Intergular-gular sulci: (0) straight, (1) curved.

Character 103. Inframarginals: (0) narrower; (1) roughly equal to; (2) wider than ventral exposure of marginals.

Character 104. Size: (0) large (carapace width 300 mm or greater, skull basal length greater than 60 mm; Neurankylus-sized); (1) small (carapace width less than 300 mm, skull basal length 60 mm or less; Plesiobaena-sized).

Appendix 2

Specimens and literature used to score taxa for phylogenetic analysis. Asterisk (*) indicates specimens examined from published material only.

(a) Neurankylus taxa scored for all characters:

Neurankylus eximius: CMN 1504* (Hay 1908; Gaffney 1972; probably Dinosaur Park Formation), AMNH 6098 (Judith River Formation), ROM 854 (probably Dinosaur Park Formation), ROM 1943 (probably Dinosaur Park Formation), TMP 1989.036.0112 (Dinosaur Park Formation), TMP 1999.055.0134 (Dinosaur Park Formation), TMP 2003.012.0171 (Dinosaur Park Formation), UALVP 30824 (Dinosaur Park Formation).

Neurankylus lithographicus (all specimens from Milk River Formation): TMP 2007.035.0045, TMP 1991.113.0001, TMP 1991.113.0009, TMP 1994.377.0001, TMP 1998.102.0014, TMP 2007.036.0001.

Neurankylus baueri (all specimens from Kirtland Formation): USNM 8344*(Gilmore 1916), PMU.R24* (Wiman 1933), PMU.R25* (Wiman 1933), PMU.R26* (Wiman 1933), PMU.R27* (Wiman 1933).

Neurankylus wyomingensis: USNM 7581* (Gilmore 1919; Upper Colorado Group).

Other Neurankylus specimens: ROM 864 (probably Kirtland Formation), YPM 8239 (Lance Formation).

(b) New taxa scored for all characters:

Arundelemys dardeni: USNM 497740* (Lipka et al. 2006; Arundel clay of Potomac Formation).

Dinochelys whitei: DNM 986* (Gaffney 1979), BYU 13099* (Brinkman et al. 2000); both Morrison Formation.

Dorsetochelys delairi: DORCM G23* (Evans and Kemp 1976; Purbeck Limestone Group).

“Dorsetochelys” buzzops: TGM 5001* (Bakker 1998; Morrison Formation).

Thescelus insiliens: AMNH 1108* and AMNH 6139* (Gaffney 1972; Hell Creek Formation).

Uluops uluops: CPS 100* (Carpenter and Bakker 1990; Morrison Formation).

(c) Other specimens scored for new characters:

Pleurosternon bullockii: BMNH 28618* (Milner 2004), BMNH R911* (Milner 2004), UMZC T1041* (Evans and Kemp 1975); all Purbeck Limestone Group.

Glyptops plicatulus: AMNH 336* and AMNH 5458* (Gaffney 1979; Morrison Formation).

Trinitichelys hiatti: MCZ 4070* (Gaffney 1972; Trinity Sands of Trinity Group).

Plesiobaena antiqua: TMP 1999.055.0145* and TMP 1985.058.0045* (Brinkman 2003b; Dinosaur Park Formation).

Peckemys brinkman: UMMP 20490* (Lyson and Joyce 2009b; Hell Creek Formation).

Cedrobaena putorius: FMNH PR 2258* (Lyson and Joyce 2009b; Hell Creek Formation).

Boremys pulchra: CMN 2281*, CMN 1130* (Gaffney 1972), TMP 1988.002.0010* (Brinkman and Nicholls 1991); all Dinosaur Park Formation).

Boremys grandis: USNM 12979* (Gilmore 1935; Kirtland Formation).

Eubaena cephalica: YPM 1785* (Gaffney 1972; Lance Formation).

Palatobaena cohen: YPM 57498*, YPM 57498*, MRF 123* (Lyson and Joyce 2009a; Hell Creek Formation).

Palatobaena bairdi: PU 16839* (Gaffney 1972; Fort Union Formation).

Palatobaena gaffneyi: UCMP 114529* (Archibald and Hutchison 1979; Wasatch Formation).

Stygiochelys estesi: AMNH 2601* (Gaffney 1972; Hell Creek Formation).

Baena arenosa: MCZ 4072* (Willwood Formation), AMNH 5977* (Gaffney 1972; Bridger Formation).

Chisternon undatum: AMNH 5961* (Gaffney 1972; Bridger Formation).

Appendix 3

Character-taxon matrix of baenid turtles used for parsimony and Bayesian analyses. Asterisk (*) denotes character retained for Bayesian analysis, but removed for parsimony analysis.

  1. [1]

    Pleurosternon bullockii 0010000000 0000000000 000?0?0000 00?0?00000 0(0*)0000(0*)000 0000000000 00(0*)0000100 0000-00?(0*)? ?001102100 00011?0?10 10?0

  2. [2]

    Glyptops plicatulus 0110010000 0000000000 000?0?0000 00?0000100 0(0*)0000(0*)000 0000000000 00(0*)0000000 0?00-000(0*)0 0000000000 0000101110 1000

  3. [3]

    Dinochelys whitei ??1000???? ?000000?0? 0????????? ?????00000 0(0*)0000(0*)000 ?10101000? ??(?*)?0???0? ??00????(?*)? ?001000000 1000110110 00-1

  4. [4]

    Dorsetochelys delairi 001000?001 0000000100 0000?10200 2????10100 1(0*)0000(0*)00? ????0?0000 0?(?*)0001201 0?00110?(0*)? ?000100000 00001?1??? ???0

  5. [5]

    “Dorsetochelys” buzzops 110001?0?0 0000000000 00?1?10111 1?00?????? ?(?*)????(?*)??? ????????00 0?(?*)0000201 0??0?001(0*)1 1??0?????? ?????????? ???1

  6. [6]

    Uluops uluops 110000?0?0 0000000000 0011?1021? 1????????? ?(?*)????(?*)??? ????????00 0?(?*)0000201 0??0110?(0*)? ?????????? ?????????? ???1

  7. [7]

    Arundelemys dardeni 000000?000 000011001- 100?000210 21???????? ?(?*)????(?*)??? ????????00 00(?*)0010201 21?11001(?*)1 100??????? ?????????? ???1

  8. [8]

    Trinitichelys hiatti 0000001000 0001000100 10001002?? 21??????00 ?(0*)0000(?*)000 110?000000 00(?*)00000100 10010001(0*)? 11100001?1 ?00?1????0 1001

  9. [9]

    Neurankylus eximius 10???0???? ??00100??? ?101???211 21???00100 0(0*)0000(0*)010 120(01)0100?? ??(?*)0?100?1 11011101(0*)1 1101111121 0010110111 1110

  10. [10]

    Neurankylus baueri ?????????? ?????????? ?????????? ?????10100 0(0*)0000(0*)000 ?2000000?? ??(?*)??????? ??0?????(?*)? ???1111101 11(01)10010(01)0 1010

  11. [11]

    Neurankylus ROM 864 ?????????? ?????????? ?????????? ??????0100 0(0*)0000(0*)0?0 ?1000100?? ??(?*)??????? ??0?????(?*)? ???10111?1 01??1010?0 1100

  12. [12]

    Neurankylus lithographicus 0????????? ?????????? ?????0021? 21??????00 0(0*)0000(?*)0?0 ?0000?00?? ??(?*)0?????? ?1011100(?*)0 0??1?1?1?1 01??200010 ?010

  13. [13]

    Neurankylus wyomingensis ?????????? ?????????? ?????????? ?????0010? 0(?*)?0??(0*)0?? ???0?0???? ??(?*)??????? ????????(?*)? ???001???1 0????????? ??10

  14. [14]

    Lance Formation Neurankylus ?????????? ?????????? ?????????? ?????10000 0(?*)0000(0*)0?? ???01100?? ??(?*)??????? ????????(?*)? ???10101?1 0????0000? ??10

  15. [15]

    Thescelus insiliens 100??0??0? 0000021100 100??0121? 20???00100 0(0*)1000(0*)001 1211010100 00(0*)0000?00 1001101?(0*)? ?011000000 00??111112 1120

  16. [16]

    Plesiobaena antiqua 1000001011 01(02)1101010 1000110111 1001011210 1(0*)0000(0*)011 121(01)010100 00(0*)1000100 2011010?(0*)? ?011000110 00(01)1111102 0121

  17. [17]

    Peckemys brinkman 1000001011 0??1111110 1000100211 100111?200 1(0*)1000(0*)001 121?0?0000 00(0*)1200100 10011011(0*)1 1??10001?0 00???1??0 --21

  18. [18]

    Cedrobaena putorius 1000011111 1??1111100 111011(01)211 1001?????? ?(?*)????(?*)??? ????????00 00(0*)0001010 10?1111?(0*)? ?????????? ?????????? ???1

  19. [19]

    Boremys pulchra 111000?10? 0101101?00 1000?00211 1010031201 1(0*)1(01)01(1*)101 1110111100 00(0*)0000100 2001110?(1*)? ?011000100 1001101112 0021

  20. [20]

    Boremys grandis ?????????? ?????????? ?????????? ?????31201 1(0*)1011(0*)100 11101111?? ??(?*)??????? ??0?????(?*)? ???1001120 0???111112 1120

  21. [21]

    Eubaena cephalica 1110102100 0101121000 1000300211 10???????? ?(?*)????(?*)??? ????????00 00(0*)0110100 10?1110?(0*)? ?00??????? ?????????? ???1

  22. [22]

    Palatobaena cohen 2000012111 1122011110 1000210211 10011?1210 ?(0*)0000(0*)011 1211110111 11(0*)1111110 20111101(0*)1 1111000100 00??01??1 --21

  23. [23]

    Palatobaena bairdi 2000012111 1122111210 1110210211 10011????? ?(?*)????(?*)??? ????????11 11(0*)0111210 0??11101(0*)1 111??????? ?????????? ???1

  24. [24]

    Palatobaena gaffneyi 2000112111 1122111110 1110210111 10???????? ?(?*)????(?*)??? ????????11 11(0*)0111210 ?1?11101(0*)1 101??????? ?????????? ???1

  25. [25]

    Stygiochelys estesi 1101001110 1112101100 1001001111 11???????? ?(?*)1111(?*)0?0 ?21?1?0100 00(0*)0100100 20?10101(0*)1 101??????? ?????????? ???1

  26. [26]

    Baena arenosa 1101001110 01?2101201 0111000211 1121021200 1(1*)1101(0*)000 1211110100 00(0*)0000001 0?11110?(0*)? ?011002110 0011010102 1121

  27. [27]

    Chisternon undatum 1101001110 0112101201 0011001111 1120021201 1(0*)1111(0*)001 1211110100 00(0*)0010101 1001100?(0*)? ?011002110 ?0?0001112 1010

  28. [28]

    Gammerabaena sonsalla ?000011110 111102101? ??1??10211 10???????? ?(?*)????(?*)??? ?????0??00 00(1*)?11??10 ????????(?*)? ?????????? ?????????? ????

  29. [29]

    Goleremys mckennai 1000001100 0102101210 10??100211 10???????? ?(?*)????(?*)??? ????????01 00(0*)000??00 ????????(?*)? ?????????? ?????????? ????

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Larson, D.W., Longrich, N.R., Evans, D.C., Ryan, M.J. (2013). A New Species of Neurankylus from the Milk River Formation (Cretaceous: Santonian) of Alberta, Canada, and a Revision of the Type Species N. eximius . In: Brinkman, D., Holroyd, P., Gardner, J. (eds) Morphology and Evolution of Turtles. Vertebrate Paleobiology and Paleoanthropology. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-4309-0_21

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