摘要
Quadrapyrgites is a microfossil reported with embryonic and post-embryonic stages from the lower Cambrian small shelly fauna of South China,and is closely related to Olivooides.Their development mode and systematic positions are hot topics in palaeoembryology and evolutionary biology in recent years,but are still under debate.Here,we present a description on the growth pattern and post-embryonic development of Quadrapyrgites quadratacris recovered from the lower Cambrian of South China.The growth zone of Q.quadratacris is situated at the oral end,and new terminal lobes are generated within the oral aperture.The terminal lobes are first in control of the opening and closure of the tubes,and later transferred to be crests,thus elongating the tubes.The post-embryonic development is characterized by a one-by-one addition of crests on the post-embryonic tissue,and an ontogenetic sequence with crest number from 1 to 17 is reconstructed.During the ontogeny,the embryonic tissue remains stable in size and morphology.The oral aperture is the only opening of the tubes,while a possible anus on the apical end does not occur.Quadrapyrgites was proposed to be the sister group of Olivooides,and now this is strengthened by the identical growth pattern and post-embryonic development.The comprehensive data from anatomy,growth pattern and post-embryonic development reject the stemlineage cycloneuralian affinity for Quadrapyrgites and Olivooides,and instead support a coronate scyphozoan hypothesis.
Quadrapyrgites is a microfossil reported with embryonic and post-embryonic stages from the lower Cambrian small shelly fauna of South China, and is closely related to Olivooides. Their development mode and systematic positions are hot topics in palaeoembryology and evolutionary biology in recent years, but are still under debate. Here, we present a description on the growth pattern and post-embryonic development of Quadrapyrgites quadratacris recovered from the lower Cambrian of South China. The growth zone of Q. quadratacris is situated at the oral end, and new terminal lobes are generated within the oral aperture. The terminal lobes are first in control of the opening and closure of the tubes, and later transferred to be crests, thus elongating the tubes. The post-embryonic development is characterized by a one-by-one addition of crests on the post-embryonic tissue, and an ontogenetic sequence with crest number from 1 to 17 is reconstructed. During the ontogeny, the embryonic tissue remains stable in size and morphology. The oral aperture is the only opening of the tubes, while a possible anus on the apical end does not occur. Quadrapyrgites was proposed to be the sister group of Olivooides, and now this is strengthened bythe identical growth pattern ment. The comprehensive pattern and post-embryonic and post-embryonic developdata from anatomy, growth development reject the stemlineage cycloneuralian affinity for Quadrapyrgites and Olivooides, and instead support a coronate scyphozoan hypothesis.
基金
supported by the National Natural Science Foundation of China(41072012 and 41102003)
the State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences(113115and 20132107)
the Key Project of Central University Fund(CHD2012ZD017)
The Ninth‘‘Challenge Cup’’Competition of College Students’Extracurricular Academic and Technological Achievements,Chang’an University,College students’ innovative entrepreneurial training program(201410710144 and 201410710105)
