Cambrian (Stage 4 to Wuliuan) brachiopods from Sonora, Mexico

Abstract

The Cambrian successions at the Chihuarruita Hill outcrop, Sonora, Mexico, have yielded two successive linguliform brachiopod assemblages that are transitional between Cambrian Stage 4 and the newly recognized global Wuliuan Stage. The lowermost assemblage includes Dictyonina sp., Paterina sp., Eothele sp., Hadrotreta rara? (Cooper), and Linnarssonia arellanoi? (Cooper), coming from the upper part of the Buelna Formation. The younger, recently named El Gavilán Formation contains a more diverse linguliform brachiopod assemblage, including Acrothele concava Cooper, Batenevotreta? mexicana n. sp., Dictyonina minutipuncta Cooper, Eothele sp., Eoobolus sp., Hadrotreta rara? (Cooper), Linnarssonia arellanoi? (Cooper), Micromitra sp., Paterina sp., and Prototreta sp. The El Gavilán Formation contains a diverse trilobite fauna suggesting Delamaran age in terms of the Laurentian regional stratigraphical scheme. The base of the global Wuliuan Stage and Miaolingian Series is defined by the first occurrence of Oryctocephalus indicus; in the absence of the index species, the base should be provisionally placed at the base of the El Gavilán Formation. The Wuliuan age of the brachiopod assemblage recovered from the El Gavilán Formation is supported by the occurrence of Acrothele in the Cambrian biostratigraphical succession of Himalaya, where the genus makes its first appearance in the Kaotaia prachina Zone. In addition, the co-occurrences of Acrothele and Eothele can be taken as an indication of the Wuliuan age of the fauna. A new biogeographic analysis confirms that the Eothele Fauna first appeared at the end of Cambrian Stage 4, as a result of increased faunal migration within the southern tropical latitudes directed from Australasian Gondwana to Laurentia. UUID: http://zoobank.org/6598f51f-cb07-4df3-bd1f-025a13e64edf

The First Report of the Acrotretoid Brachiopod Hadrotreta from the Tsinghsutung Formation Cambrian (Series 2, Stage 4), Guizhou, South China

“…At present, Hadrotreta is currently known to be from Nevada [ 18 , 40 , 41 , 42 , 52 ], California [ 28 ], Pennsylvania [ 22 ], Canada [ 25 ], the Himalayas [ 23 ], Australia [ 20 , 24 ], Turkestan [ 16 ], Uzbekistan [ 17 ], Novaya Zemlya [ 26 , 37 ], Kazakhstan [ 19 ], Argentina [ 29 ], the Far East [ 21 ], and Mexico [ 27 ], from sites with a geological age ranging from Cambrian Age 4 to the Miaolingian Epoch ( Figure 5 a). Hadrotreta occurred in Pennsylvania, Nevada, Canada, and Mexico during the Cambrian Age 4 ( Figure 5 a), where it was located in Laurentia ( Figure 5 b).…”

“… Maps of stratigraphic occurrence, geographical, and palaeogeographical distribution of the acrotretoid brachiopod Hadrotreta in the Cambrian. ( a ) Stratigraphic occurrence and geographical distribution of the acrotretoid brachiopod Hadrotreta in Cambrian (Cambrian Stage 4 and Miaolingian are marked by light grey and dark grey shades, respectively); and ( b ) palaeogeographical distribution of the acrotretoid brachiopod Hadrotreta , the palaeogeographical map modified from Holmer et al [ 27 ]. The numbers such as ①–⑩ of ( a , b ) show the distribution of Hadrotreta [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 37 , 40 , 41 , 42 , 52 ].…”

“…Zhang et al [ 5 , 12 , 13 ] not only studied the relationship between the ontogenetic stage of Eohadrotreta , their distribution of epidermal cells, and the attachment area of their soft body, but also explored the systematic relationship between Eohadrotreta and other lingulid brachiopods, providing an excellent basis for further research on the early origin and expansion of brachiopods. As one of the oldest and most cosmopolitan acrotretoids, Hadrotreta has been reported from the Cambrian Series 2 to Miaolingian in Nevada, California, Pennsylvania, Canada, Turkestan, Uzbekistan, Novaya Zemlya, Kazakhstan, the Far East, Australia, the Himalayas, and Mexico [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. In addition, Hadrotreta ?…”