Wyulda, Alexander, 1918

Schwartz, Leah R. S., 2016, A revised faunal list and geological setting for Bullock Creek, a Camfieldian site from the Northern Territory of Australia, Memoirs of Museum Victoria 74, pp. 263-290 : 277-287

Genus WYULDA

cf. ASHERJOELI sp. Crosby, Nagy and Archer 2001

( Fig. 17 , table 5)

Referred Material – NTMAG P87110-36 left P3; NTMAG

P87110-37 right M1/2; NTMAG P87110-38 right M2/3.

Locality and Horizon – Top Site, Small Hills, Tm8 the Top Site beds of the Camfield beds.

Determination. P87110-36, which is a left P3, is nearly identical to that described for Wyulda asherjoeli Crosby, Nagy and Archer 2001 from the Mike’s Menagerie site at Riversleigh. It differs from this species only in having a more acute angle to the buccal cingulum. P87110-37, a right M1/2, and P87110-38, a right M2/3 are phenetically similar and nearly identical, in both structure and wear pattern. Like P87110-36, these teeth most closely resemble Wyulda asherjoeli .

Family PETAURIDAE (Bonaparte, 1838) Archer 1984

PETAURIDAE indet.

( Figs. 18A, B , table 6)

Referred Material – NTMAG P8697-7 left M1?

Locality and Horizon – Dromornithid Mountain, Small Hills, Tm4 the Dromornithid Mountain beds of the Camfield beds.

Determination. P8697-7 is assigned to the Petauridae due to its near-square occlusal outline, low-crowned nature, and the indistinctness of the cusps, all of which are peaturid characteristics. It differs from the modern Petaurus australis Shaw 1791 in the absence of an enlarged stylar shelf, and from Petaurus norfolcensis Kerr 1792 in its possession of a metaloph. This structure however, unites it with the petaurids known from the Pliocene Hamilton Local Fauna (Victoria) ( Turnbull et al., 1987), although in P8697-7 both the protocone and hypocone (figs. 18A, B) are significantly smaller than the buccal cusps. No crenulations are present in the central basin of the tooth, although these may have been removed by wear.

Family PSEUDOCHEIRIDAE ( Winge, 1893) Archer (1984)

PSEUDOCHEIRIDAE indet.

( Figs. 18C–F , table 7)

Referred Material – NTMAG P9464-249 right M2; NTMAG

9276-1 right M2; NTMAG P9464-245 left m2/3.

Locality and Horizon – Top Site, Small Hills, Tm8 the Top Site beds of the Camfield beds.

Determination. P9276-1 and P9464-249 are identical except that P9276-1 is less worn than P9464-249. These teeth display the characteristic offset of the postprotocrista and premetaconule cristathatWoodburneetal.(1987) suggestedwassynapomorphic for Pseudocheiridae (figs. 18 C-F). They differ from species of Pildra in having a more pronounced paraconule and neometaconule, and in being lower-crowned. They differ from species of Marlu in having a paraconule that does not extend to the midpoint of the tooth’s occlusal surface, and in the arcuate shape of the neometaconule. They differ from species of Paljara in having a much less ‘W-shaped’ ectoloph.

For P9464-245, the presence of a hypoconulid, a larger entostylid, and a mostly linear (rather than arcuate) entostylid ridge separate this tooth from Pildra antiquus Woodburne, Tedford and Archer 1987 from the Pinpa Local Fauna of the Namba Formation which has been correlated with the middle Oligocene Zone A of the Etadunna Formation of South Australia. The entoconid here is developed in a more bladelike fashion than in Pildra secundus Woodburne, Tedford and Archer 1987 , from the Etadunna Formation late Oligocene Zone B, and the entostylid ridge is here directed almost transversely, rather than antero-buccally.

This tooth appears most similar to Pildra tertius Woodburne, Tedford and Archer 1987 , from the early Miocene Kutjumarpu Local Fauna, however it is significantly larger and somewhat more ornate in its crenulations. Like species of Pildra , it differs from Marlu in possessing an entostylid ridge; having an indistinct paraconid; lacking an entoconid that is aligned en echelon with the metastylid; and the absence of a cusp-like structure on the lingual side of the anterior end of the cristid obliqua. It differs from species of Paljara in having a strongly developed entostylid ridge, and in being larger. This tooth could be considered a larger, more derived species of Pildra .

PHALANGERIDA indet.

( Fig. 20 , table 8)

Referred Material – NTMAG P9215-12 right m1; NTMAG

P9215-11 right m2.

Locality and Horizon – Top Site, Small Hills, Tm8 the Top Site beds of the Camfield beds.

Determination. P9215-12 is similar to that of Djaludjangi yadjana Brammal 1998 , however it also shows affinities to the pilkpildridids. No protostylid is present on this tooth, separating it from Djilgaringa gillespiei Archer, Tedford and Rich 1987 ; however, like that species, there is a short ‘flattened’ section to the trigonid extending anteriorly from the protoconid. This feature is not present in D. yadjana . The lack of a metaconid separates this tooth from both species of Djilgaringa and those of Pilkipildra . This tooth further differs from both species of Pilkipildra in that the cristid obliqua does not ascend the flank of the trigonid, and there is no notch in the anterior cingulum for articulation of the p3. It differs from D. yadjana in the presence of the deep fissure between the trigonid and the talonid observed on the lingual side of the tooth; not possessing a ‘complete’ hypolophid as well as the posterior cingulid; and having much more crenulate enamel. This tooth is assigned to Phalangerida incertae sedis, pending review of this group.

On P9215-11, the trigonid and talonid are equal widths, implying, by comparison with Djilgaringa gillespiei , that this is an m2. This tooth is very similar to P9215-12, and fits together with it in such a way as to imply that these teeth are from the same individual. No comparisons of this tooth with Djilgaringa thompsoni Archer, Tedford and Rich 1987 or with Pilkipildra taylori Archer, Tedford and Rich 1987 are possible as these species are known only from m1s. It differs from D. gillespiei in having a distinct paraconid; in the transverse ridge from the metaconid not contacting the protoconid; in lacking a metastylid and possessing an entostylid; and in having a continuous cristid obliqua. This tooth also differs from Pilkipildra handi in its possession of a transverse cristid on the talonid and the presence of crenulations on the trigonid basin.

P9215-11 differs from Djaludjangi yadjana in not having complete ‘lophids’, and in being less ‘pinched in’ at the ‘waist’ (between the talonid and trigonid) of the tooth than that D. yadjana . The position of the entoconid in P9215-11 also differs slightly from that of D. yadjana , being slightly posterior of that cuspid. D. yadjana also lacks an entostylid or the secondary accessory stylid on the entoconid, in both of which features it is similar to Djilgaringa gillespieae . However, the presence of a paraconid separates this tooth from both D. yadjana and D. gillespieae , although on the latter species there is a small ‘wobble’ in the anterior cingulid, discernible in buccal view, that could be interpreted to represent this cuspid. Like P9215-12, this tooth is assigned to the Phalangerida incertae sedis, pending review of this group.

Comment. A large diversity of ‘possum’ groups is recorded at Bullock Creek. Unfortunately, many of the groups described here are in dire need of review, a problem that extends even to the living pseudocheirid species. Changes in organisation of many of the groups discussed may affect the familial interrelationships presented here, and in some cases, may synonymise the groups used here. For example, Flannery et al. (1987) synonymised Wyulda with Trichosurus , although this has not been followed by subsequent authors ( Crosby et al., 2001).

The presence of Wyulda sp. cf asherjoeli at Bullock Creek suggests a possible correlation between this site and the early Miocene Camel Sputum Riversleigh site in which it is found ( Crosby et al., 2001; Woodhead et al., 2015). However, there is only one other species of Wyulda known, an extant form, Wyulda squamicaudata , which implies that either that the genus is fairly conservative, or that those features recognised as ‘trichosurine’ are plesiomorphic for Phalangeridae (Beck, pers. comm.).

The absence of the final phalangeroid family, the Ektopodontidae , from the Bullock Creek local fauna is puzzling. While this family is known to be relatively rare in the Cenozoic deposits of Australia, its continued absence from this site contrasts with its otherwise widespread occurrences.

What may be the oldest petaurid is also recorded here at Bullock Creek, though Tedford and Kemp (1998) referred material from the late Oligocene Geilston Bay site to Petauroidea incertae sedis. However, the association of the Bullock Creek tooth with the Petauridae is tentative. The only other fossil record of this family is the similarly tentatively assigned Hamilton petaurids ( Turnbull et al., 1987). Unfortunately, as it is only an isolated tooth and already simplified along petaurid lines, very little information as to its phylogenetic affinities may be obtained without further material.

The pseudocheirid upper molars listed here are likely to represent a new genus, however they are unlikely to be associated with the lower molar, as the uppers are clearly separate to both Pildra and Paljara , genera with which the lower shows some similarity. The use of the presence of the entostylid ridge to separate Marlu and Pildra species has been thrown into some doubt by Roberts et al. (2009), who identified an entostylid ridge on the m1 of Marlu praecursor and noted the probable paraphyly of that genus. Further, Roberts et al. (2008) noted that features distinguishing the posterior molars of Pildra and Paljara species are minor and often removed by wear. There is some possibility, then, than the lower molar reported here belongs to either Pildra or Paljara , but such a determination will have to wait on further material.

Therefore, it is probable that at least two separate species of pseudocheirid are present at Bullock Creek. Up to nine undescribed species have apparently been found in a single Riversleigh site ( Archer, 1992), and co-existence of pseudocheirid species has been recorded at Riversleigh, in zone D, latest Oligocene, of the Etadunna Formation, and in the early Miocene Wipajiri Formation ( Woodburne et al., 1993). Thus, the co-existence of two pseudocheirid species in the Bullock Creek Local Fauna is not surprising.

Superfamily MACROPODOIDEA Gray 1821

Family MACROPODIDAE Gray 1821

cf. PALAEOPOTOROUS Flannery and Rich 1986

( Figs. 21 , 22 )

Referred Material – NTMAG P8670-22 left M2/3; NTMAG P908-78 left M2/3; NTMAG P87106-2 right M2/3; NTMAG P9464- 243 right M2.

Locality and Horizon – P8670-22 unrecorded quarry in the Camfield beds; P908-78 Blast Site, Small Hills, Tm2 the Blast Site beds of the Camfield beds; P87106-2 Site Y, Small Hills, Tm1 the XY beds of the Camfield beds; P9464-243 Top Site, Small Hills, Tm8 the Top Site beds of the Camfield beds.

Determination. P87106-2 shows strong resemblance to NMV P172995, except that it is slightly larger. Similarly, P908-78 resembles NMV P172999. Both these teeth were described by Flannery and Rich (1986) as belonging to Palaeopotorous priscus Flannery and Rich 1986 , from the late Oligocene Namba Formation of South Australia. These teeth differ from the upper molar figured by those authors, which has both complete lophs that incorporate a third cusp. Either P. priscus shows a large amount of variation along the molar row in terms of numbers and expression of stylar cusps, and the form of the protoloph, in which case these teeth could be considered to belong to a closely related species with a similar level of variation; or, both the material referred to P. priscus , and these teeth, represent a number of closely related species.

P9464-243 contains three cusps in the metaloph, a characteristic of those teeth described above and referred to Palaeopotorous . Like P908-78, and species of Ekaltadeta , it also shows a stylar crest. This tooth is therefore included with the other teeth referred to Palaeopotorous and considered to represent a possible link between this genus and units of the Propleopinae. It is also similar to the upper teeth described for Wanburoo hilarus Cooke 1999 , a bulungamayine, except that W. hilarus possesses a stylar cusp C.

Subfamily BULUNGAMAYINAE Flannery, Archer and Plane 1983

( Figs. 23–25 , table 10)

Referred Material – NTMAG P9464-192 left i1; NTMAG P87105- 29 left p2; NTMAG P9464-218 right p2; NTMAG P9272-10 left dp3; NTMAG P2786-1 left P3 and partial palate; NTMAG P9272-11 left p3; NTMAG P8697-8 right M2/3; NTMAG P874-1 left M3; NTMAG P9464-217 right m2; NTMAG P9464-190 left m2.

Locality and Horizon – P9464-192, P9464-218, P9464-217, P9464- 190 Top Site, Small Hills, in Tm8 the Top Site beds of the Camfield beds; P87105-29, P9272-10, P9272-11, P874-1 unrecorded quarry of the Camfield beds; P2786-1 Horseshoe West, unnamed unit of the Camfield beds; P8697-8 Dromornithid Mountain, Small Hills, in Tm4 Dromornithid Mountain beds of the Camfield beds.

Determination. Incisors. i1 is unknown in most Miocene kangaroos, and so comparison with P9464-192 is difficult. Confinement of enamel to the buccal surface of the tooth, combined with the presence of dorsal and enamel flanges, and the absence of enamel ridges suggests that this tooth may belong to the Bulungamayinae ( Cooke, 1997a) .

Premolars. P87105-29 and P9464-218 are most similar to bulungamayine premolars, in that they are finely ridged and not ‘bulbous’ in the same way as the premolars of balbarines and hypsiprymnodontids, with transcristids that continue to the base of the tooth. They are broadly similar to dp2s known for Wanburoo hilarus , a bulungamayine kangaroo. P2786-1 is assigned to the Bulungamayinae on the basis of its length as it is much longer than premolars known for Balbarinae. The presence of a posterolingual cuspule also unites this tooth with the bulungamayines, although this is also a feature of macropodines (Cooke, 1999). If, as Kear and Cook (2001) and Prideaux and Warburton(2010) contend, Bulungamayinae is best considered a paraphyletic grade of macropodids, including forms closer to Stenurinae and to Macropodinae, this is unsurprising.

For P9272-11, both the curvature and length of this premolar unite it with the bulungamayines. Short bulbous premolars, such as those seen in hypsiprymnodontids and balbarines are considered plesiomorphic for macropodoids, with elongate premolars a derived condition displayed in bulungamayines and macropodines (Cooke, 1999).

Molars. P8697-8, P874-1 and P9272-10 are all tentatively referred to the Bulungamayinae on the basis of the ‘bulbous’ base of the molar relative to those of balbarines. ‘Bulbous’ molars appear so because the loph/ids of the tooth do not extend to the edges of the tooth. This is not the case in balbarines, however it is seen in bulungamayines. On P9272- 10 there is also a buccally directed crest from the entoconid that unites it with bulungamayines. On P9464-217 there is a well-developed cristid obliqua, which originates at the hypoconid, heads antero-lingually until flexing in the interlophid valley to contact the base of the protoconid. This is reminiscent of that seen in potoroids, but on P9464-217, the cristid obliqua intersects the protolophid, rather than being continuous with the anterior cingulid as it is in potoroids.

The presence of an anterobuccally directed ridge on the entoconid unites P9464-217 with the Bulungamayinae , as its presence indicates a bulungamayine-style formation of the hypolophid, as per Cooke (1997b). This tooth also shows the ‘bulbous’ characteristic of bulungamayine molars.

P9464-190 is also ‘bulbous’ which indicates it may belong to the Bulungamayinae . A pre-entocristid, such as is present on this tooth, can be found in both balbarine and bulungamayine molars, however it is somewhat more common in the bulungamayine, being present at every stage of Cooke’s (1997b) hypothesis of hypolophid development, rather than simply at one stage, as is the case in balbarines ( Cooke, 1997c).

Family BALBARIDAE ( Flannery, Archer and Plane, 1983) Cooke and Kear 1999

( Figs. 26–28 , table 11)

Referred Material – QVMAG.17 right i1; NTMAG P907-57 right i1; NTMAG 9464-3 right i1, partial; NTMAG P9464-216 right p3; NTMAG P8695-80 left p3, partial; NTMAG P8692-5 right M4; NTMAG P925-13 left M4; NTMAG P8612-4 right m3; NTMAG P9464-2 right m2.

Determinations. Incisors. QVMAG.17, P907-57 and P9464-3 are referred to the Balbaridae on the basis of possessing branching enamel ridges (see Cooke, 1992 and discussion below). QVMAG.17 is quite a robust tooth, and quite a bit larger in size than the others (table 11). P907-57 is unique from the other two in preserving both dorsal and ventral enamel flanges.

Premolars. P9464-216 is relatively short antero-posteriorly, and has quite coarse ridges. The smaller number of ridges and lack of occlusal convexity precludes its referral to the Hypsiprymnodontidae . This tooth is therefore fairly confidently assigned to the Balbaridae . The relatively large size of this tooth (see table 11) excludes it from any of the species for which the known premolars have the same number of ridges as this tooth (4). However it is smaller and more gracile than the premolars known for Balbaroo and Wururoo , and resembles those of Nambaroo / Ganawamaya more closely. The large size of P8695-80, its robustness and small number of cuspids relative to its size and length determines its assignment to the Balbaridae . Unlike P9464-216, this is quite a robust tooth, and so possibly of Balbaroo / Wururoo affinities, rather than Nambaroo / Ganawamaya .

Molars. There are no obvious features to unite P8692-5 with Balbaridae . However, the lophs extend the full width of the tooth, and it does not display the anterior-posterior compression characteristic of bulungamayine uppers. It is therefore tentatively considered to be a balbarine upper. Like P8692-5, no features of P925-13 clearly place it in any subfamily; however, it does have lophs that extend the full width of the tooth, and does not show any features that would preclude it belonging to the Balbaridae .

Like the M4s described above, P8612-4 shows no features that clearly unite it with any subfamily; however, it does appear similar to other balbarine lowers described here. It is fully lophodont, but lacking the ‘bulbous’ appearance that would unite it with Bulungamayinae , and so it is tentatively assigned to the Balbaridae .

P9464-2 is interpreted as balbarine on the basis of the postentocristid, which is possibly a remnant of the structure seen in Nambaroo that bounds the posterior ‘pocket’ on the hypolophid of that genus.

Comment. Most of the macropodoid teeth identified above belong to either the Balbaridae or Bulungamayinae . The exception are those teeth referred to Palaeopotorous . This genus was originally described as a new subfamily, but subsequent authors have assigned it to either the Bulungamayinae ( Kear and Cooke, 2001) the Propelopinae ( Ride, 1993), or the Potoroinae ( Prideaux, 2004) and it is considered here to be of indeterminate subfamily. No material referrable to Palaeopotorous has been found outside of the Namba Formation.

Distinguishing balbarid molars from bulungamayine molars required the use of some new criteria. For lower molars other than m1, the only characters that have been considered to differentiate balbarids from bulungamayines are: a small cuspid - possibly a rudimentary paraconid positioned on the lingual side of the anterior cingulum ( Flannery et al., 1983); the presence of a posterior cingulid; and a ‘generally pleisomorphic morphology’ ( Cooke, 1992).

The presence of a posterior cingulid distinguishes the Balbaridae from the Bulungamayinae , however the absence of one does not preclude inclusion with the Balbaridae , as some plesiomorphic balbarids lack a posterior cingulid. Cooke’s (1997a) observation that bulungamayine molars retain a remnant of the bunolophodont hypolophid in the form of an anterobuccally directed cristid on the anterior face of the entoconid provides another criterion for recognising bulungamayines. However, this is only true of plesiomorphic bulungamayines, with other, advanced bulungamayines having lost this cristid.

For the upper molars of the two groups, there are even fewer synapomorphies that can be used to distinguish them. Cooke (1999) suggested that bulungamayines as a general rule retain only stylar cusp C on the upper molars, while balbarids retain both stylar cusps C and D. More apomorphic members of both groups show no stylar cusps at all. However, a single stylar cusp is a characteristic of teeth referred to Propleopinae and Palaeopotorous . Under Kear and Cooke’s (2001) classification, this genus is a member of Bulungamayinae .

Stylar cusps are a plesiomorphic feature of the australidelphian, and the diprotodontian tooth. Cooke (1997b) suggests that the bulungamayine ancestor had lost stylar cusp D, and was therefore, in this aspect, more derived than the balbarid ancestor. However, stylar cusp D also appears to have been lost in the ancestor of the propleopines.

During the course of this study, it was observed that balbarid uppers are generally more elongate than those belonging to bulungamayines, and that, along with the ‘bulbous’ nature of the molar in question, was used to assign upper teeth. ‘Bulbous’ is used to describe the condition in which the loph/ids of the tooth, whether lower or upper, do not extend for the full width of the molar. This is the condition observed universally in bulungamayines (as defined here). In balbarids, by contrast, the loph/ids extend fully to the buccal and lingual edges of the tooth.

Incisors have previously been used to distinguish between balbarid and bulungamayines, with the concentration of enamel on the buccal side of the tooth considered a bulungamayine character, while thick enamel over both sides is considered a balbarid character. The presence of branching enamel ridges on the dorsolingual side of i1 was described by Cooke (1992) on Ganawamaya ornata . Two different incisors are described here, both of which display branching enamel ridges in the position described by Cooke. Neither of these incisors can be referred to G. ornata , as they are less gracile than those described for that species. These ridges are consistently present in undescribed material from both the Kutjumarpu Local Fauna and Riversleigh (pers. obs.), and always occur in balbarids.

Figures

Figure 17. Stereopairs of occlusal views of teeth referred to Wyulda sp. cf. asherjoeli. a, b, NTMAG P87110-36 LP3; c, d, NTMAG P87110-37 RM1/2; e, f, NTMAG P87110-38 RM2/3. Scale bar = 3 mm.

Figure 18. Occlusal stereopairs of petauroid upper molars. a, b, NTMAG P8697-7, petaurid LM1; c, d, NTMAG P9464-249, pseudocheirid RM2; e, f, NTMAG P9276-1, pseudocheirid RM2. Scale bar = 2 mm.

Figure 20. Molars referred to Phalangerida incertae sedis. a, b, occlusal stereopair of NTMAG P9215-12, Rm1; c, d, occlusal stereopair of NTMAG 9215-11, Rm2; e, lingual view of NTMAG P9215-11; f, lingual view of NTMAG P9215-12; g, buccal view of NTMAG P9215-11. Scale bar = 2 mm.

Figure 21. Upper molars referred to cf. Palaeopotorous. a, b, occlusal stereopair of NTMAG P8670-22, LM2/3; c, buccal view; d, lingual view; e, f, occlusal stereopair of NTMAG P908-78, LM2/3; g, buccal view; h, lingual view; i, j, occlusal stereopair of NTMAG P87106-2, RM2/3; k, buccal view; l, lingual view. Scale bar = 3 mm.

Figure 22. Occlusal stereopair of NTMAG P9464-243, RM2 of cf. Palepotorous. Scale bar = 3 mm.

Figure 23. Occlusal stereopair of NTMAG P9464-218, bulungamayine Rp2. Scale bar = 3 mm.

Figure 24. Bulungamayine P3s and p3s. a, b, occlusal stereopair of NTMAG P2786-1, LP3; c, d, occlusal stereopair of NTMAG P8663-3, Rp3; e, f, occlusal stereopair of NTMAG P9272-11, Lp3. Scale bar = 12 mm for a and b, 6 mm for c-f.

Figure 25. Bulungamayine molariform teeth. a, b, occlusal stereopair of NTMAG P8697-8, RM2/3; c, d, occlusal stereopair of NTMAG P874-1, LM3; e, f, occlusal stereopair of NTMAG P9464-190, Lm2; g, h, occlusal stereopair of NTMAG P9464-217, Rm2; i, j, occlusal stereopair of NTMAG P9272-10, Ldp3. Scale bar = 3 mm.

Figure 26. Stereopair of ventral view of balbarine incisors. a, b, QVMAG.17, Ri1; c, d, NTMAG P907-57, Ri1. Scale bar = 10 mm.