A diverse assemblage of monotremes (Monotremata) from the Cenomanian Lightning Ridge fauna of New South Wales, Australia

Figures & data

Fig. 1. Map of Australia showing the location of Lightning Ridge and nearby localities. A, Lightning Ridge. B, Tank 5 and Olga’s Dam sites. Adapted from Hart et al. 2021.

Fig. 2. AM F132596-9, dentary of Opalios splendens gen. et sp. nov. in A, B, occlusal, C, D, buccal, and E, F, lingual views. The internal morphology of the mandibular canal is shown in both G, distal oblique and H, mesial oblique views. G and H are not to scale. Art = articular facet of dentary. Mc = mandibular canal. Mf = mental foramen. Sym = symphysis.

Table 1. Measurements for monotreme specimens mentioned in the text.

	Measurement (mm)
Opalios splendens. Holotype. AMF 132599 –132599.
Length of preserved portion of dentary	66.0
Estimated length of complete dentary	76.0
AM F132597
Depth of dentary below posterior alveolus m5	9.2
Width of dentary at posterior alveolus m5	6.4
Length of alveoli for m5	5.1
Length posterior alveolus of m5	3.6
Width of posterior alveolus of m5	3.5
Length of anterior alveolus of m5	2.6
Width of anterior alveolus of m5	4.0
Length of anterior alveolus of m4	2.3
Width of anterior alveolus of m4	3.0
Length of m4	6.4
AM F132598
Depth of dentary at posterior alveolus of m1	8.9
Width of dentary at posterior alveolus of m1	5.6
Length of alveoli of m2	5.2
Length of posterior alveolus of m2	3.2
Width of posterior alveolus of m2	3.2
Length anterior alveolus of m2	2.3
Width anterior alveolus of m2	2.7
Length of alveoli of m1	4.3
Width of posterior alveolus of m1	2.8
Length of anterior alveolus of m1	2.4
Width of anterior alveolus of m1	2.5
AMF 132599.
Dentary depth below anterior root ant premolar	7.8
Length of alveoli, p2	6.1
Length of alveoli, p1	5.8
Length of diastema one.	3.2
Length of diastema two (incomplete)	3.7
Dentary width below the anterior root of p1	4.4
Dharragarra aurora. Holotype. AM F97262
Depth of dentary below posterior alveoli of m2	7.7
Width of dentary at posterior alveoli of m2	5.7
Dentary depth at anterior alveolus of m2	7.4
Dentary width at anterior alveolus of m2	5.5
Dentary depth at posterior margin of dental foramen	7.1
Dentary width at posterior margin of dental foramen	4.8
Width of alveolus of m3	2.1
Estimated length of alveolus of m3	2.4
Length of alveoli of m2	7.2
Length of posterior alveolus of m2	4.6
Width of posterior alveolus of m2	3.5
Length of anterior alveolus of m2	2.6
Width of anterior alveolus of m2	3.5
Length of alveoli of m1	7.0
Length of posterior alveolus, of ml	4.2
Width of posterior alveolus of m1	4.0
Length of anterior alveolus of m1	2.3
Width of anterior alveolus of m1	3.1
Alveolar length of p4	4.1
Alveolar length of p3	5.4
Alveolar length of p2	4.8
Dentary depth below posterior root of p4	8.1
Dentary width below posterior root of p4	5.1
Parvopalus clytiei. Holotype. AM F 161198
Total length of dentary fragment	14.7
Depth of dentary below posterior alveolus of posterior molar	4.8
Width of dentary below posterior alveolus of posterior molar	3.2
Length of alveoli of posterior molar	3.2
Length of posterior alveolus of posterior molar	1.8
Width of posterior alveolus of posterior molar	1.9
Length of anterior alveolus of posterior molar	1.3
Width of anterior alveolus of posterior molar	2.3
Steropodon galmani. Holotype. AM F66763
Depth of dentary below posterior of m3	8.3
Breadth of dentary below posterior of m3 (broken so this is a minimum)	5.7
m3 length	5.0
m2 length	6.6
m1 length	7.3
AM F 97263
Depth of dentary at anterior alveolus m3	7.2
Width of dentary at anterior alveolus m3	5.9
Length of alveoli for m2	7.5
Length of posterior alveolus of m2	3.9
Width of posterior alveolus of m2	3.6
Length of anterior alveolus of m2	3.0
Width of anterior alveolus of m2	3.7
AM F161197
Depth of dentary below posterior root of m3	7.7
Width of dentary at posterior root of m3	6.1
Length of alveoli of m3	5.1
Length posterior of alveolus of m3	3.2
Width of posterior alveolus of m3	2.1
Length of anterior alveolus of m3	2.6
Width of anterior alveolus of m3	3.3
Approximate length of alveoli of m2	7.4
Length of posterior alveolus of m2	4.4
Width of posterior alveolus of m2	3.3

Fig. 3. AM F97262, dentary of Dharragarra aurora gen. et sp. nov. in A, B, occlusal, C, D, buccal and E, F, lingual views. Mf = mental foramen.

Fig. 4. Steropodon galmani AM F97263 in A, B, occlusal, C, D, buccal and E, F, lingual views. Steropodon galmani AM F161197 in G, H, occlusal, I, J, buccal and K, L, lingual views.

Fig. 5. AM F161198, dentary of Parvopalus clytiei gen. et sp. nov. in A, B, occlusal, C, D, buccal and E, F, lingual views. Maf = mandibular foramen. Ar = ascending ramus.

Fig. 6. Cross sections of the mandible scaled to similar sizes. A, Parvopalus clytiei (AM F161198) at the anterior of m3, B, Steropodon galmani (AM F161197) in between m2 and m3, C, Dharragarra aurora (AM F97262) in between m2 and m3, D, Steropodon galmani (AM F97263) in between m2 and m3, E, Opalios splendens (AM F132598) in between m1 and m2. The white line indicates the mandibular canal.

Table 2. Number of known specimens per monotreme taxon, Lightning Ridge local fauna.

Family	Genus	Species	No. of known specimens
?Teinolophidae	Stirtodon	elizabethae	1
Kollikodontidae	Kollikodon	ritchiei	2
Steropodontidae	Steropodon	galmani	3
?Steropodontidae	Parvopalus	clytiei	1
?Ornithorhynchidae	Dharragarra	aurora	1
Opalionidae	Opalios	splendens	1

Hart, L., Bell, P., Smith, E., Mitchell, D., Brougham, T. & Salisbury, S., 2021. A probable skeleton of Isisfordia (Crocodyliformes) and additional crocodyliform remains from the Griman Creek Formation (Cenomanian, New South Wales, Australia). Journal of Paleontology 95, 351–366.

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