New early Cambrian sclerites ofLapworthella schodakensisfrom NE Greenland: advancements in knowledge of lapworthellid taxonomy, sclerite growth and scleritome organization

AbstractThe Cambrian Stage 4 upper Bastion Formation of Albert Heim Bjerge and CH Ostenfeld Nunatak, NE Greenland, yielded 34 excellently preserved sclerites ofLapworthella schodackensisamong other small shelly fossils. Lapworthellids have been interpreted as members of the camenellans, a basal tommotiid group. Little is known about this group although the morphological and ultrastructural features of their sclerites allow a potential reconstruction of a lophophorate body plan. The exquisite material from Greenland provides significant new data for the revision of the species taxonomy, but also for the comprehension of the scleritome structure of lapworthellids and the mode of formation of their sclerites. Two morphotypes ofL. schodackensissclerites are identified: one with a simple apex, occurring in sinistral and dextral forms; and one bilaterally symmetrical sclerite with two apices. All bear a similar ornamentation constructed of repeated growth sets consisting of a reticulate inter-rib groove with tubercles, a densely denticulate rib and a striated sub-rib area. The new data on the ornamentation and observations of the laminar shell microstructure ofL. schodackensisenable us to improve the reconstruction of growth in lapworthellids. Finally, the morphological features of the two types of sclerites provide new information for the reconstruction of the bilaterally symmetrical multi-component lapworthellid scleritome with evidence of the fusion of adjacent sclerites during early ontogeny.

Download Full-text

First discovery of Small Shelly Fossils and new occurrences of brachiopods and trilobites from the early Cambrian (Stage 4) of the Swedish Caledonides, Lapland

GFF ◽

10.1080/11035897.2021.1895303 ◽

2021 ◽

pp. 1-17

Author(s):

Christian B. Skovsted ◽

Timothy P. Topper ◽

Stephen McLoughlin ◽

Ove Johansson ◽

Fan Liu ◽

...

Keyword(s):

Early Cambrian ◽

Small Shelly Fossils ◽

Stage 4 ◽

New Occurrences

Download Full-text

Humble origins for a successful strategy: complete enrolment in early Cambrian olenellid trilobites

Biology Letters ◽

10.1098/rsbl.2013.0679 ◽

2013 ◽

Vol 9 (5) ◽

pp. 20130679 ◽

Cited By ~ 13

Author(s):

Javier Ortega-Hernández ◽

Jorge Esteve ◽

Nicholas J. Butterfield

Keyword(s):

Environmental Conditions ◽

Fossil Record ◽

Direct Evidence ◽

Morphological Features ◽

Early Cambrian ◽

Defence Mechanism ◽

Successful Strategy ◽

New Information ◽

Adverse Environmental Conditions ◽

Morphological Ability

Trilobites are typified by the behavioural and morphological ability to enrol their bodies, most probably as a defence mechanism against adverse environmental conditions or predators. Although most trilobites could enrol at least partially, there is uncertainty about whether olenellids—among the most phylogenetically and stratigraphically basal representatives—could perform this behaviour because of their poorly caudalized trunk and scarcity of coaptative devices. Here, we report complete—but not encapsulating—enrolment for the olenellid genus Mummaspis from the early Cambrian Mural Formation in Alberta, the earliest direct evidence of this strategy in the fossil record of polymerid trilobites. Complete enrolment in olenellids was achieved through a combination of ancestral morphological features, and thus provides new information on the character polarity associated with this key trilobite adaptation.

Download Full-text

Mobergellans from the early Cambrian of Greenland and Labrador: new morphological details and implications for the functional morphology of mobergellans

Journal of Paleontology ◽

10.1017/jpa.2017.41 ◽

2017 ◽

Vol 92 (1) ◽

pp. 71-79 ◽

Cited By ~ 3

Author(s):

Christian B. Skovsted ◽

Timothy P. Topper

Keyword(s):

Functional Morphology ◽

Lower Cambrian ◽

Growth Direction ◽

Morphological Features ◽

Larval Shell ◽

Early Cambrian ◽

Shell Material ◽

Muscle Attachment ◽

Stage 4

AbstractNew morphological features of the mobergellan Discinella micans (Billings, 1871) from the lower Cambrian (Stage 4) of Northeast Greenland and southern Labrador are described. The new features include: (1) the morphology of the larval shell, which is shown to be cap-shaped, subcircular, and with impressions of the internal muscle attachment scars; (2) a range of unusual shell deformations (changes in growth direction resulting in thickened shells, partial detachment of shell laminae and subsequent regrowth, internal projections of shell material increasing the depth of the shell by up to 150%, disturbances and irregular fusion of muscle scars). In addition, we provide new details about the variability in number and shape of the anteriormost internal muscle scars, which often fuse and may vary in number from one to three (resulting in nine to 11 scars in total). Together the new observations provide additional strength for the hypothesis that mobergellan shells represent opercula of an as yet unknown tubular organism.

Download Full-text

New artiopodan arthropods from the early Cambrian Emu Bay Shale Konservat-Lagerstätte of South Australia

Journal of Paleontology ◽

10.1666/11-077.1 ◽

2012 ◽

Vol 86 (2) ◽

pp. 340-357 ◽

Cited By ~ 27

Author(s):

John R. Paterson ◽

Diego C. García-Bellido ◽

Gregory D. Edgecombe

Keyword(s):

Alimentary Tract ◽

Three Dimensional ◽

Cladistic Analysis ◽

South Australia ◽

First Record ◽

Early Cambrian ◽

Burgess Shale ◽

Early Devonian ◽

New Information ◽

Stage 4

The Emu Bay Shale Konservat-Lagerstätte (Cambrian Series 2, Stage 4) on Kangaroo Island, South Australia, is the source of two new non-biomineralized artiopodan arthropods. Squamacula buckorum n. sp. is the first record outside of China of a genus otherwise known only from its type species, S. clypeata, from the Chengjiang biota. The Australian species displays the long cephalic doublure and spiniform exopod setae that are apomorphic for this genus, provides new information on the alimentary tract and midgut glands (the latter preserved as three-dimensional, permineralized structures), and indicates interspecific variability in trunk segment numbers. The distribution of Squamacula strengthens the biogeographic connections between early Cambrian “Burgess Shale-type” biotas of Australia and South China. Australimicola spriggi n. gen. n. sp. represents a monotypic genus resolved in a cladistic analysis of Cambro-Ordovician artiopodans as most closely related to or within Conciliterga (a clade containing Helmetia, Kuamaia, Kwanyinaspis, Rhombicalvaria, Saperion, Skioldia, and Tegopelte). Compared with other members of this clade from Chengjiang and the Burgess Shale, the new genus is diagnosed by an elongate trunk with 23 thoracic tergites having spatulate pleural tips and a small pygidium possessing a single, elongate pair of pleural spines, with specimens also showing a hypostome attached to an anterior (or prehypostomal) sclerite, antennae, short endopods, an annulated alimentary tract, and a series of three-dimensional, permineralized midgut glands. An alternative relationship between Australimicola and the Early Ordovician–Early Devonian Cheloniellida explains the shared anterior flexure of trunk pleurae but forces dubious homologies in other characters, such as dorsally-articulated furcae versus spines.

Download Full-text

Early Cambrian brachiopods and other shelly fossils from the basal Kinzers Formation of Pennsylvania

Journal of Paleontology ◽

10.1017/s0022336000058467 ◽

2010 ◽

Vol 84 (4) ◽

pp. 754-762 ◽

Cited By ~ 10

Author(s):

Christian B. Skovsted ◽

John S. Peel

Keyword(s):

New York ◽

Shell Structure ◽

Early Cambrian ◽

Small Shelly Fossils ◽

Stage 4 ◽

Eastern Shelf

An assemblage of seventeen species of Small Shelly Fossils, dominated by the brachiopod Eothele tubulus and species of the mollusk Yochelcionella, is described from the basal Kinzers Formation of Thomasville, Pennsylvania. The occurrence extends southwards the distribution of an Early Cambrian fauna (Cambrian Series 2, Stage 4) that is otherwise characteristic of the eastern shelf of Laurentia from New York to Greenland. The poorly known acrothelid brachiopod Eothele tubulus is redescribed based on large collections of ventral valves. The shell structure of E. tubulus is characterized by orthogonal baculae, and represents the oldest known example of a baculate shell structure, indicating that this type of shell structure evolved already in the Early Cambrian.

Download Full-text

An outer shelf shelly fauna from Cambrian Series 2 (Stage 4) of North Greenland (Laurentia)

Journal of Paleontology ◽

10.1017/jpa.2020.112 ◽

2021 ◽

Vol 95 (S83) ◽

pp. 1-41

Author(s):

John S. Peel

Keyword(s):

New York ◽

New Species ◽

North America ◽

World Wide ◽

Wide Distribution ◽

East Greenland ◽

North East ◽

Small Shelly Fossils ◽

Stage 4 ◽

North Greenland

AbstractAn assemblage of 50 species of small shelly fossils is described from Cambrian Series 2 (Stage 4) strata in North Greenland, the present day northernmost part of the paleocontinent of Laurentia. The fossils are derived from the basal member of the Aftenstjernesø Formation at Navarana Fjord, northern Lauge Koch Land, a condensed unit that accumulated in a sediment-starved outer ramp setting in the transarctic Franklinian Basin, on the Innuitian margin of Laurentia. Most other small shelly fossil assemblages of similar age and composition from North America are described from the Iapetan margin of Laurentia, from North-East Greenland south to Pennsylvania. Trilobites are uncommon, but include Serrodiscus. The Australian bradoriid Spinospitella is represented by a complete shield. Obolella crassa is the only common brachiopod. Hyoliths, including Cassitella, Conotheca, Neogloborilus, and Triplicatella, are abundant and diverse, but most are represented just by opercula. Sclerites interpreted as stem-group aculiferans (sachitids) are conspicuous, including Qaleruaqia, the oldest described paleoloricate, Ocruranus?, Inughuitoconus n. gen., and Hippopharangites. Helcionelloid mollusks are diverse, but not common; they are associated with numerous specimens of the bivalve Pojetaia runnegari. The fauna compares best with that of the upper Bastion Formation of North-East Greenland, the Forteau Formation of western Newfoundland, and the Browns Pond Formation of New York, but several taxa have a world-wide distribution. Many specimens are encrusted with crystals of authigenic albite. New species: Anabarella? navaranae, Stenotheca? higginsi, Figurina? polaris, Hippopharangites groenlandicus, Inughuitoconus borealis, and Ocruranus? kangerluk.UUID: http://zoobank.org/160a17b1-3166-4fcf-9849-a3cabd1e04a3

Download Full-text

Tarimspirafrom the Cambrian (Series 2, Stage 4) of Laurentia (Greenland): extending the skeletal record of paraconodontid vertebrates

Journal of Paleontology ◽

10.1017/jpa.2018.68 ◽

2018 ◽

Vol 93 (1) ◽

pp. 115-125

Author(s):

John S. Peel

Keyword(s):

New Species ◽

Type Species ◽

Weak Acid ◽

Early Cambrian ◽

Basal Cavity ◽

Stage 4 ◽

First Time ◽

A New Species ◽

North Greenland

AbstractPhosphatic sclerites of the problematicTarimspiraYue and Gao, 1992 (Cambrian Series 2) recovered by weak acid maceration of limestones display a unique range of mainly strongly coiled morphologies. They were likely organized into multielement scleritomes, but the nature of these is poorly known; some sclerites may have had a grasping function.Tarimspirasclerites grew by basal accretion in an analogous fashion to younger paraconodonts (Cambrian Series 3–4) but lack a basal cavity. Based on proposed homologies,Tarimspiramay provide an extension of the early vertebrate paraconodont–euconodont clade back into the early Cambrian.Tarimspirais described for the first time from Laurentia (North Greenland), extending its known range from China and Siberia in Cambrian Series 2. In addition to the type species,Tarimspira planaYue and Gao, 1992, the Greenland record ofTarimspiraincludes two morphotypes of a new species,Tarimspira artemi.UUID:http://zoobank.org/c7c536c8-cdaf-49a9-ae1d-77c392f553fc.

Download Full-text

Analysis of beak morphometry of the horned octopus Eledone cirrhosa (Cephalopoda: Octopoda) in the Thracian Sea (NE Mediterranean)

Mediterranean Marine Science ◽

10.12681/mms.219 ◽

2004 ◽

Vol 5 (1) ◽

pp. 143 ◽

Cited By ~ 9

Author(s):

E. LEFKADITOU ◽

P. BEKAS

Keyword(s):

Body Weight ◽

High Resistance ◽

Growth Pattern ◽

Size Estimation ◽

Digestive Process ◽

Lower Beak ◽

New Information ◽

Ne Mediterranean ◽

Hard Structures ◽

Species Taxonomy

Cephalopod beaks are chitinous structures situated in the buccal mass lying at the base of their arms. Because they are among the few hard structures of cephalopods with high resistance to erosion during digestive process in predator stomachs, the study of the beak morphometry is of major importance for the species taxonomy, as well as, for the size estimation of the cephalopods consumed. In this study new information is provided on the dimensions and pigmentation process of the upper and lower beak of the horned octopus Eledone cirrhosa derived from 67 female and 47 male specimens caught by trawl in the Thracian Sea (NE Mediterranean). The growth of both beaks was allometric in relation to the mantle length and body weight. According to the results of covariance analysis, no difference was found in growth pattern of beaks between sexes. Four degrees of pigmentation were identified in both upper and lower beaks, the darkening process starting in females at a smaller size.

Download Full-text