Ontogeny of the Furongian (late Cambrian) remopleuridioid trilobiteHaniwa quadrataKobayashi, 1933 from Korea: implications for trilobite taxonomy

Abstract

The monophyly of the trilobite Order Asaphida has been challenged. The Superfamily Remopleuridioidea was included in the Order Asaphida, based on the ventral median suture and highly bulbous protaspis of the late Furongian–Tremadocian representatives of the group. The remopleuridioid,Haniwa quadrataKobayashi, 1933 from the Furongian (late Cambrian) Hwajeol Formation of Korea, represents a primitive morphology of the Remopleuridioidea. This trilobite does not have a typical globular morphology of asaphoid protaspis, and the free cheeks remained yoked together during the whole of the development. This supports the previous proposition that the Superfamily Remopleuridioidea should be excluded from the Order Asaphida. In addition, the evolution of a highly globular protaspis of the Ordovician remopleuridioid trilobites from the less bulbous protaspis corroborates the possibility of multiple evolutions of a highly globular protaspis. It can be argued that the possession of a highly globular protaspis does not guarantee the membership of the Order Asaphida, and thus the concept of the Order Asaphida should be emended.

Post‐embryonic development of the Early Ordovician (ca. 480 Ma) trilobite Apatokephalus latilimbatus Peng, 1990 and the evolution of metamorphosis

“…Protaspides of the both species are spherical with three large pairs of sharp, conical spines, and have a very narrow ventral opening due to the highly enrolled morphology for free‐swimming life mode. In contrast, a Furongian (Late Cambrian) remopleuridioidean did not entail “asaphoid protaspis” in its development (Park and Choi ). Therefore, there must have been a de novo evolution of the “asaphoid protaspis,” and the rise of indirect development, within the remopleuridioidean lineage between the Furongian and the late Tremadocian.…”

Furongian (late Cambrian) trilobites from the Asioptychaspis subglobosa Zone of the Hwajeol Formation, Korea

“…A complete ontogenetic description of this species was given by Park & Choi (2011a) and is not repeated here. As pointed out by Park & Choi (2011a), Sohn & Choi (2007) mistakenly regarded all the Haniwa specimens from both the Asioptychaspis Zone and the overlying Quadraticephalus Zone as H. sosanensis Kobayashi, 1933. However, H. sosanensis has a parallel-sided anterior branch of the facial suture, whereas the cranidia from the Asioptychaspis subglobosa Zone invariably have forward divergent anterior branches of the facial suture.…”

“…1; see Park & Choi, 2011a for locality map). Sohn & Choi (2007) established the Asioptychaspis Zone using the material collected from this locality.…”

“…Because only Asioptychaspis morphology has been discovered in North China (see Chough et al, 2010, Kim 2012, the biozone name 'Ptychaspis'-Tsinania Zone should be changed to the Asioptychaspis-Tsinania Zone. Park & Choi (2009, 2011a documented the ontogeny of Tsinania canens (Walcott, 1905), Asioptychaspis subglobosa (Sun, 1924) and Haniwa quadrata Kobayashi, 1933, respectively, based on the material recovered from this part of the Hwajeol Formation.…”

Pelagic or benthic? Mode of life of the remopleuridid trilobite Hypodicranotus striatulus

“…Unique to this form is the planktonic protaspid growth stages, and earlier meraspid stages (Chatternton & Speyer 1997). A number of studies have precluded a benthic life style on the basis that the larval body size was less than a millimetre, with three dimensionally extending long spines (e.g., Whittington 1959, Fortey & Chatterton 1988, Chatterton & Speyer 1997, Park & Choi 2011. These morphological features fulfil the general requirement for a planktonic life style because it had a large surface area in relation to its volume (e.g., Ruppert et al 2003).…”