Supplementary Information v410 574 Morphological Characters Used in the Phylogenetic Analysis
Coding of extant salamander groups based on our observation of representative specimens of each group, and data presented in several publications (Wake & Ozeti 1969; Duellman & Trueb 1986; Wake & Larson 1987; Trueb 1993; Larson 1991; Sever 1991; Shubin & Wake 1996; Larson & Dimmick 1993). New characters added in this paper are denoted with “*”. Coding of Karaurus based on Ivachnenko (1978), and Valdotriton on Evans & Milner (1996).
1. Premaxillae: separate (0); or fused (1). Variable states of this character are found in plethodontids (Wake & Larson 1987), salamandrids (Wake & Ozeti 1969), and hynobiids (Duellman & Trueb 1986; Larson 1991; contra Trueb 1993).
2. Dorsal process of premaxilla: absent or poorly defined with only partial contact with the nasal bone (0); well-defined, intervening nasals or dorsally overlapping nasals (1); strong posterior extension both contacting the frontal and separating the nasals (2); extension of dorsal process deeply intervenes the frontals (3); posterior extension of dorsal process contacts the frontal lateral to the nasal (4). Modified from Duellman & Trueb (1986: character B). Coding of Dicamptodontidae based on Cope (1889). Valdotriton has a well-developed dorsal process of the premaxilla overlapping the nasal but not contacting the frontal (Evans & Milner 1996).
3. Maxilla: present in adults as normal element of maxillary arcade (0); greatly reduced as a rudimentary element (1); entirely absent and functionally replaced by modified vomer (2). Duellman & Trueb (1986: character C). Larson (1991: 248): Only in the family Proteidae are these bones uniformly absent. Two derived states are observed in different species of the Sirenidae (Estes 1965) with state (1) interpreted to be apomorphic for the family.
4. Septomaxilla: present (0); absent (1). The septomaxilla is absent in the Amphiumidae, Cryptobranchidae, Proteidae, Salamandridae, and Sirenidae (Lapage 1928; Wake 1966). The variant conditions observed in plethodontids are associated with paedomorphosis or asymmetrical development of the right and left jaws (Wake 1966); the septomaxilla appears to be primitively present in the family (Larson 1991).
5. Nasal ossification: paired nasals present with sutural midline contact or fused (0); nasals separate without midline contact (1); nasal absent (2). Larson (1991) combined this character with another (dorsal process of the premaxilla); we treat these as independent characters, because no logical overlapping of the characters across the basic taxa occurred in our matrix.
6. Lacrimal: present (0); absent (1). Karaurus has a lacrimal (Ivachnenko 1978) and the presence of this element in urodeles is coded as a primitive condition; however, the distribution of the (0) state among extant urodele groups (Hynobiidae, Rhyacotritonidae, and Dicamptodontidae) indicates the character is probably more complex than the simple present and absent conditions (Worthington & Wake 1971; Larson 1991; Good & Wake 1992; Laurin 1998). Within the Cryptobranchidae, variant conditions are observed in some specimens of Andrias (present in AMNH 58074, 104411; absent in AMNH 57991).
7. Quadratojugal: present (0); absent (1). See different character description and coding in Laurin (1998).
8. Prootic/exoccipital/opisthotic fusion: three separate elements (0); prootic/exoccipital fused, separate opisthotic (1); all three elements fused (2). Modified from Duellman & Trueb (1986: character H), Trueb (1993: character 1); see comments on the character in Larson (1991).
9. Pterygoid: present, triradiate and boomerang-shaped (0); enlarged with distinct anteromedial process (1); present as straight bar with loss of anterolateral process (2); or absent (3).
10. Internal carotid foramen: present (0); absent (1). The internal carotid foramen opens in the lateral alae of the parasphenoid in Karaurus, and several urodele groups including primitive hynobiids (e.g., Liua and Batrachuperus; see Zhang 1985; Trueb 1993). The derived condition is encountered in several extant families including Plethodontidae, Salamandridae, Sirenidae, and some ambystomatids (Duellman & Trueb 1986). The foramen is also absent in Valdotriton (S. E. Evans, pers. comm. 1998). Conflicting interpretations of cryptobranchids exist within the literature (Estes 1981; Trueb 1993), but our observation of several specimens in AMNH comparative material shows both Andrias and Cryptobranchus have well-defined internal carotid foramina.
11. Prefrontal: present (0); absent (1).
12. Basilaris complex of inner ear: presence of both recessus basilaris (0); loss of papillae (1); loss of entire basilaris complex (2).
13. Angular/prearticular fusion: angular is separate and distinct from the prearticular (0); angular fused to prearticular (1). Among extant urodeles, a separate angular bone is present in the cryptobranchids and hynobiids (see Duellman & Trueb 1986; Trueb 1993: angular present or absent in hynobiids). Srinivasachar (1962) considered Rhyacotriton to retain an angular, whereas other authors (Good & Wake 1992; Trueb 1993) coded the angular as being absent in the genus. The angular of Karaurus is diagnosed in the following manner: “the angular is fused with the prearticular” but is described later in the paper as “the long and narrow angular is separated from the prearticular by a suture.” As the angular is clearly labeled in the line drawing of the holotype (Ivachneneko 1978: fig. 1a), and the drawing concurs with the description, we interpret the angular is present for this taxon (see also Estes 1981). Both the taxa known from the Fengshan sample have a free angular bone in the lower jaw.
14. Coronoid: present as a separate element (0); absent in adult stage (1).
15. Articular: present as separate element (0); fused with prearticular (1).
16. First hypobranchial and first ceratobranchial: the two bones retain are separate (0); two elements fused (1). The derived condition is known for Amphiumidae (Erdman & Cundall 1984; Trueb 1993), and Hynobiidae (Noble 1931; Trueb 1993). Conflicting interpretations of the condition of cryptobranchids exist (Jollie 1973; Duellman & Trueb 1986; Larson 1991; Trueb 1993). The first hypobranchial and the first ceratobranchial are unfused in some specimens of Andrias (Cope 1889: pl. XIII-4) and some Cryptobranchus (Chang 1968: pl. II-fig. 6c). Other specimens (e.g., AMNH 55996: Cryptobranchus alleganiensis) posess an ossified first hypobranchial but retain a cartilaginous first ceratobranchial. We have coded the variant states present in cryptobranchids accordingly.
17. Ceratobranchial II in adults: present (0); or absent (1).
18. Premaxillary teeth: present (0); absent (1).
19. Palatal dentition: confined to vomer (0); extended to cover parasphenoid (1).
20. Vertebral centrum: amphicoelous (0); opisthocoelous (1).
21. Four-faceted articulation of exoccipital and atlas: absent (0); present (1).
22. Postatlantal ribs: bicapitate (0); unicapitate (1).
23. Atlantal spinal nerve foramen: absent (0); present (1).
24. Postatalantal spinal nerve foramina: all postatalantal spinal nerves exit intervertebrally (0); spinal nerve foramina present on some caudal vertebrae (1); foramina present on all caudal and sacral vertebrae (2); foramina occur in trunk, sacral and caudal series (3).
25. Stapes: present in adults (0); absent in adults (1).
26. Lateral wall of nasal capsule: complete (0); incomplete (1).
27. Lateral narial fenestra: absent (0); present (1).
28. Posterior wall of nasal capsule: complete (0); incomplete (1).
29. Nasal-lacrimal duct: present (0); absent (1).
*30. Dermal sculpture on skull roof: present (0); absent (1).
*31. Frontal anterior extension: frontal does not extend lateral to nasal bone (0); or does extend to lateral border of nasal (1).
*32. Medial border of orbit: formed mainly by frontal (0); frontal excluded from entering orbit (1).
*33. Frontal/maxillary contact: frontal and maxilla separated by prefrontal (0); frontal contacts dorsal process of maxilla (1); contact absent because of loss of maxilla (2).
*34. Anterolateral process of parietal: weakly developed or absent (0); strongly elongated process extending lateral to frontal (1).
*35. Squamosal orientation in dorsal view: mediolaterally oriented as a transverse bar (0); anteroposteriorly inclined or parallel to skull midline (1).
*36. Exposure of prootic-exoccipital-opisthotic complex in dorsal view: the complex largely concealed by parietal or exposed posterior to skull table (0); large exposure extends lateral to parietal table (1).
*37. Squamosal contact with the parietal or other roofing elements: contact present (0); or absent (1).
38. Origin of M. adductor mandibulae internus superficialis: on dorsolateral surface of parietal (0); origin extends posteriorly to exoccipital (1); origin extends to cervical vertebra (2); origin extends anteriorly towards level of frontal (3).
39. Ypsiloid cartilage: present (0); absent (1).
40. Fusion of distal carpal 1+2: fusion absent (0); or fusion present (1).
41. Fusion of distal tarsal 1+2: fusion absent (0); or fusion present (1).
42. Number of centralia in manus or pes: more than one central element (0); or one central element (1).
43. Intermedium and ulnare: intermedium separate (0); fused to ulnare (1).
44. Distal carpal 4 and distal carpal 5: two elements remain separate (0); two elements fused (1).
45. Haploid chromosome number: more than 20 (0); reduced to 19 (1); further reduced to 14 or less (2).
46. Diploid chromosome number: 56 or more (0); 40-55 (1); lower than 40 (2).
47. Microchromosome: present (0); absent (1).
48. Ciliated epithelium of cloaca: present in both sexes (0); present in male but absent in female (1); or absent in both sexes (2).
49. Extent of epidermis in female cloacal chamber: epidermal lining does not extend to anterior one-half of the cloacal chamber (0); or does extend into anterior one-half of the chamber (1).
50. Primary and secondary folds in the male cloacal tube and associated glands: both folds and associated glands absent (0); two groups of glands present without development of folds (1); three groups of glands present without folds (2); or two folds and all three groups of associated glands present (3).
51. Anteroventral cloacal glands: absent in both sexes (0); or present in male but absent in female (1); or present in both sexes (2).
52. Spermathecae in cloaca: absent (0); or present (1).
53. Dorsal cloacal glands: absent in both sexes (0); present in male only (1); or present in both sexes (2).
54. Posteroventral cloacal glands: absent (0); or present (1).
55. Pubotibialis and puboischiotibialis muscles: separate (0); fused (1).
56. Number of free ribs on anterior caudal vertebrae: more than three pairs (0); two to three pairs (1); or free ribs absent (2).
57. Ectopterygoid: present (0); or absent (1).
58. Postfrontal: present (0); or absent (1).
59. Scapula-coracoid ossification: ossified as separate elements (0); two elements as a single ossification (1).
60. Nasal/prefrontal contact: present (0); or absent (1).