Mesozoic

Pristification: Defining the convergent evolution of saws in sharks and rays (Chondrichthyes, Neoselachii)

TYLER GREENFIELD — Mon, 24 Jun 2024 00:00:00 +1200

Convergent evolution is the development of analogous structures or bauplans in at least two independent lineages of organisms. Convergence is driven by the occupation of similar ecological niches and by various physical and phylogenetic constraints (McGhee, 2011). Despite the wide recognition of this phenomenon in evolutionary biology, formal terms and definitions for specific examples are rare. The most notable is carcinisation, which refers to the appearances of a crab-like bauplan among crustaceans (Keiler et al., 2017). Here the term ‘pristification’ is proposed for the convergence of saws in sharks and rays. It was coined previously in a preliminary publication (Greenfield, 2021a) but is formally defined for the first time. Not only does it highlight a remarkable convergent structure, but it also serves as a template for future terminology.

**Morphological features of the Upper Cretaceous planthopper Mimaeurypterus burmiticus suggest specialization for cryptic camouflage on tree bark**

DOLEV FABRIKANT, DI-YING HUANG, CAROLIN HAUG, JOACHIM T. HAUG, YAN-ZHE FU — Mon, 24 Jun 2024 00:00:00 +1200

The extinct planthopper family Mimarachnidae is widely known in the Cretaceous of Eurasia. Two new specimens of the monotypic genus Mimaeurypterus Fu & Huang, 2021, from the early Upper Cretaceous of northern Myanmar are described. The intraspecific variation is assessed, and the description supplemented morphology of the head, pronotum, legs, and abdomen is provided. The flattened pronotum and broad forewings are interpreted as adaptations for the reduction of shadows at body margins, thus blurring the body outline of the insect and facilitating crypsis.

A new species of the family Praeaulacidae (Hymenoptera: Evanioidea) from mid-Cretaceous Kachin amber

CORENTIN JOUAULT, DI-YING HUANG — Mon, 24 Jun 2024 00:00:00 +1200

A new praeaulacid species, Habraulacus splendidus sp. nov., is described and illustrated based on a male specimen from mid-Cretaceous Kachin amber. This newly discovered taxon is, inter alia, characterised by its relatively low number of antennomeres (about 28) and its complex forewing venation (i.e., with both 2rs-m and 3rs-m present). Together with the recent discoveries of praeaulacid wasps from Kachin amber, this new species lets us assume that the family Praeaulacidae was well-diversified in Cretaceous forests. The subsequent decline of this family likely occurred either in the Late Cretaceous or, in a more optimistic scenario, during the Cenozoic era.

**A new species of Mesosticta in mid-Cretaceous Kachin amber (Odonata: Platystictidae)**

ANDRÉ NEL, CORENTIN JOUAULT, DI-YING HUANG — Mon, 24 Jun 2024 00:00:00 +1200

Mesosticta additicta sp. nov., fourth species of this platystictid genus, is described from the mid-Cretaceous Kachin amber, suggesting its endemic diversification in the West Burma Block (WBB), possibly in relation to the geographic isolation of this area during the formation of mid-Cretaceous Kachin amber.

A new genus of Mesopsychidae from the late Middle Triassic Tongchuan entomofauna and its taxonomic and palaeogeographic implications

XIN-NENG LIAN, YONG ZHANG, CHEN-YANG CAI, ZHUO FENG, DI-YING HUANG — Thu, 27 Jun 2024 00:00:00 +1200

Mesopsychids, a long-proboscid mecopteran group, are presumably associated with the pollination of Mesozoic gymnosperms. Despite over 100 years of study on the genus Mesopsyche, only isolated wings have been discovered. Mesopsyche is now redefined as a monotypic genus with only one species, Mesopsyche triareolata. The other species previously classified within Mesopsyche are have been assigned to the newly established genus Turbidapsyche Lian & Huang, gen. nov., distinguished by its three-branched Sc, in contrast to the numerous Sc branches of Mesopsyche. Herein, we present descriptions and illustrations of new material from the middle part (late Ladinian) of the Middle–Upper Triassic Yanchang Formation. We assigned these specimens to the newly erected genus, Turbidapsyche Lian & Huang, gen. nov. Turbidapsyche tongchuanensis (Hong, 2007) comb. nov., the first reported Turbidapsyche (Mesopsyche) from the Tongchuan entomofauna, is revised based on a new specimen. Additionally, we erecte three new species of Turbidapsyche Lian & Huang, gen. nov. based on their wing size, shape, and especially the coloured patterns. Turbidapsyche orientalis Lian & Huang, gen. et sp. nov. is characterised by the distinctly shrunken wing base and dense coloured markings along anterior wing. Turbidapsyche sparsanota Lian & Huang, gen. et sp. nov. is distinguished by its relatively larger wing size and sparse coloured spots situated at the forks, crossveins, and apical longitudinal veins. Turbidapsyche hongi Lian & Huang, gen. et sp. nov. is characterised by a relatively small wing size and sparser striped coloured markings. Although hindwings of Turbidapsyche Lian & Huang, gen. nov. are described and illustrated, they are not assigned to any species. Species of both Mesopsyche and Turbidapsyche are discussed in detail. The wing coloured patterns of Turbidapsyche exhibit regional differentiation, with numerous coloured spots or spots fused into striped coloured markings observed in China, transparency in Kyrgyzstan, and full pigmentation in Ukraine. Based on previous palaeomagnetic research conducted in Tongchuan area, we derive a palaeolatitude of 21° in the Middle Triassic. Turbidapsyche was distributed along the northern Palaeotethys, near a similar palaeolatitude, suggesting it inhabited comparable climates and perhaps had specific ecological requirements or limited dispersal capabilities.

Newly identified late Early Cretaceous volcanic rocks in the Beixiangshan area, Lower Yangtze River Belt, South China and its implications

Thu, 27 Jun 2024 00:00:00 +1200

The magmatic events in the Lower Yangtze River Belt could be divided into four stages: 148–133 Ma, 131–127 Ma, 127–121 Ma, and 109–100 Ma. The final episode is represented by the intrusions in the Ningzhen area, however no contemporaneous volcanic rocks have been reported. In this study, we present an integrated analysis of petrology, zircon U-Pb ages, and whole rock major-trace elements for newly identified volcanic rocks in the Beixiangshan area. Zircon U-Pb dating yields an eruption age of 106.3 ± 0.4 Ma, indicating that these rocks likely belong to the lower part of the Pukou Formation. The volcanic rocks exhibit arc-like geochemical features, distinct from those of the intrusions in the Ningzhen area. The volcanic rocks may be formed during a tectonic transition phase from compression to extension, due to the direction changes of plate convergence. The widespread angular unconformity around the volcanic rocks may represent episode C of the Yanshanian tectonic event, based on the dating work on volcanic rocks, its minimum age should be ca. 106 Ma.

The 9th International Conference on Fossil Insects, Arthropods and Amber held in Xi’an, China

DI-YING HUANG, CHEN-YANG CAI — Fri, 31 May 2024 00:00:00 +1200

At the 8^th International Conference on Fossil Insects, Arthropods and Amber (Fossil×3) held in 2019 in Santo Domingo, Dominican Republic, Professor Diying Huang, from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), won the bid to host the 9^th Fossil×3 conference in Xi’an, China. Due to the pandemic, the conference was postponed twice and was finally successfully held in the ancient city of Xi’an from April 18–25, 2024.

The 6th International Conference of Palaeogeography held in Nanjing, China

XIANG FANG — Fri, 14 Jun 2024 00:00:00 +1200

The 6^th International Conference on Palaeogeography (ICP6), which took place in China’s Nanjing from the 17^th to the 20^th of May, 2024, was a great success. This prestigious conference was jointly sponsored by the International Society of Palaeogeography, the Palaeontological Society of China, and China University of Petroleum (Beijing), and the periodical Journal of Palaeogeography (English version) and was organised by Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.

Checklist of the Triassic wood (updated June 2024)

XU-DONG GOU, ZHUO FENG — Thu, 27 Jun 2024 00:00:00 +1200

A list of all known fossil wood taxa recorded from the Triassic, up to June of 2024, is provided. The list contains 50 genera and 130 species of gymnospermous wood taxa documented from 16 countries across seven continents. Specifically, 17 genera and 27 species were reported from Asia, 10 genera and 39 species from Europe, 3 genera and 3 species from Africa, 5 genera and 6 species from North America, 21 genera and 43 species from South America, 9 genera and 16 species from Australia and 4 genera and 7 species Antarctica. Taxonomically, 7 genera and 8 species were documented from the Lower Triassic, 7 genera and 8 species from the Middle Triassic, and 37 genera and 98 species from the Upper Triassic. Systematically, 5 genera and 7 species belong to Cycadales, 1 monotypic genus belongs to Bennettitales, 2 genera and 3 species belong to Ginkgoales, 30 genera and 97 species of Coniferales, 7 genera and 12 species belong to Pteridosperms, 3 genera and 4 species belong to Cordaitales, and 3 genera and 6 species are incertae sedis.

**Occurrence of Early Cretaceous Shimakuroxylon wood in southeastern China, and its palaeobiogeographic significance**

MENG-YU CHEN, AO-WEI XIE, MIN XU, HAO WU, NING TIAN — Thu, 27 Jun 2024 00:00:00 +1200

The Mesozoic gymnosperm genus Shimakuroxylon Philippe, Boura, Oh et Pons is a peculiar petrified wood taxon which was exclusively recorded from the Jurassic–Early Cretaceous interval in eastern Asia. To date, ten occurrences of this genus were documented in Japan, Indochina and Tibet (southwestern China). However, little is known about the record of Shimakuroxylon in eastern China. Here, we describe a new fossil wood specimen from the Lower Cretaceous Laocun Formation in Longyou County of Quzhou City, Zhejiang Province, southeastern China. This fossil specimen exhibits typical Shimakuroxylon anatomy with japonicum-type (shimakurean) radial tracheid pitting and araucarioid cross-field pitting, representing a new record of Shimakuroxylon in eastern Asia. This new finding contributes to our understanding of the fossil wood diversity of the Early Cretaceous xyloflora in southern China, and provides additional data that furthers our knowledge of the palaeobiogeographical distribution of Shimakuroxylon. Shimakuroxylon is commonly suggested as an indicator of warm and wet climates based on its palaeobiogeographical distribution pattern. However, evidence from plant megafossils and sporopollen suggests the local climate of the study area was warm and arid to semiarid during the Early Cretaceous. It is tentatively suggested that the wood plant might have lived in a warm and humid basin margin with relatively sufficient water supply, though the general environmental background might have been arid to semiarid.

Discussion on the age of the Early Cretaceous amber from the Hailar Basin, NE China

Thu, 27 Jun 2024 00:00:00 +1200

Amber in China is predominantly found from the Cenozoic era, with the oldest-known amber originating from the Middle Triassic Qingyan biota in Guiyang, Guizhou. Chinese Cretaceous amber has been known from Xixia and Neixiang (Henan Province), Guangzhou (Guangdong Province), and the Buir Lake area (Inner Mongolia). Some previous studies have suggested that the amber found at the base of the Yimin Formation in the Yimin Coal Mine in the Hailar Basin (130.9 ± 2.8 Ma, as constrained by detrital zircon U-Pb dating in the original paper) represents the oldest known amber in China at that time. In this paper, detrital zircon U-Pb dating was conducted on the clastic rocks from the Damoguaihe Formation of the Zhalainuoer Coal Mine, Hailar Basin to contest the age of the Buir Lake amber. Our results suggest that the upper part of the Damoguaihe Formation was deposited earlier than 116 Ma (late Aptian), consistent with biostratigraphy and isotopic chronology. Therefore, the age of the amber-bearing Damoguaihe Formation in Hailar Basin should be slightly older than 116 Ma. Amber from the Yimin Formation was discovered from two layers, with the lower layer (the first coal seam) likely near the Aptian–Albian boundary and the upper layer slightly later than 111.7 Ma. Our analyses further confirm that Buir Lake ambers are from the upper Lower Cretaceous Damoguaihe Formation and Yimin Formation, dating to the Aptian–Albian.