Kennardiidae, Laurie, 1986

Claybourn, Thomas M., Skovsted, Christian B., Betts, Marissa J., Holmer, Lars E., Bassett-Butt, Lucy & Brock, Glenn A., 2021, Camenellan tommotiids from the Cambrian Series 2 of East Antarctica: Biostratigraphy, palaeobiogeography, and systematics, Acta Palaeontologica Polonica 66 (1), pp. 207-229 : 224-226

publication ID	https://doi.org/ 10.4202/app.00758.2020
persistent identifier	https://treatment.plazi.org/id/5509C270-FFB5-3B20-FF9E-BE14FEE618CF
treatment provided by	Felipe
scientific name	Kennardiidae
status

Treatment

Kennardiidae indet.

Fig. 10 View Fig .

1990 Kennardia sp. A ; Evans and Rowell 1990: 699, fig. 7.9.

1990 Kennardia sp. B ; Evans and Rowell 1990: 699, figs. 7.10–7.12.

Material.— One symmetrical first sclerite type ( KUMIP 585077 , 1 figured), one symmetrical second sclerite type KUMIP 585082 , 1 figured) and seven asymmetrical third sclerite types ( KUMIP 233002 , 585078–585081 , 585083 , 585084 , 6 figured) from M section, northern Holyoake Range ( Fig. 1 View Fig , Table 2; Evans and Rowell 1990). Numerous fragments were also recovered from this section ( Table 2). Cambrian Series 2, Stages 3–4 .

Description.—Three identifiable sclerite types. First sclerite type symmetrical, low, curved over the ventral field and quadrangular in transverse section ( Fig. 10A View Fig ). Second sclerite type coniform, symmetrical, tall, straight and hexagonal in transverse section ( Fig. 10G View Fig ). Third sclerite type coniform, asymmetrical, tall, coiled over the ventral field, and triangular in transverse section ( Fig. 10B–F, H, I View Fig ). Sclerites with a distinctive growth set of wide, wall-like comarginal ribs and inter-rib grooves.

The first sclerite type symmetrical with dorsal field lacking plicae and with no clear distinction from the lateral fields ( Fig. 10A View Fig 1 View Fig ) which have a single, weakly developed plica bound by furrows ( Fig. 10A View Fig 3 View Fig ). Ventral field is flat and straight, lacking plicae ( Fig. 10A View Fig 2 View Fig ). The sclerite is coiled only at the apex where it overhangs the ventral field Fig. 10A View Fig 2 View Fig ). Growth series forming wall-like comarginal ribs, well-developed and present on entire sclerite surface, following the transverse profile of the sclerite.

The second sclerite type known from single, poorly preserved sclerite. The anterior field is gently curved laterally with two weakly developed plicae ( Fig. 10G View Fig 1 View Fig ). Lateral fields triangular in shape, flat and straight, lacking plicae Fig. 10G View Fig 1 View Fig , G 3 View Fig ). Posterior field side triangular and straight, lacking plicae ( Fig. 10G View Fig 2 View Fig ). Growth sets developed on the entire sclerite surface and follow the transverse profile of the sclerite on the dorsal side and lateral fields. The growth sets on the ventral side curve upwards into broad inverted U-shape ( Fig. 10G View Fig 2 View Fig ).

The third sclerite type is tall, triangular, asymmetrical with a concave ventral surface and convex dorsal surface in smaller specimens, but curves back towards the dorsal side in larger specimens ( Fig. 10E View Fig 1, H 1 View Fig ). The ventral side has a series (3–7) of well-developed radial plicae with the outmost bordering the proximal and distal edges ( Fig. 10C View Fig 2 View Fig , D 1 View Fig , E 3 View Fig , E 4 View Fig , F 1, H 1 View Fig ). The proximal edge is shorter than the distal edge. The dorsal side has a single, large and broad plication in larger specimens ( Fig. 10C View Fig 1 View Fig , D 2, H 2 View Fig , H 3 View Fig ). The fields bounded by the central plication and the proximal edge is flat or slightly concave ( Fig. 10D View Fig 2 View Fig , H 1 View Fig ). The field bounded by the central plication and distal edge is convex ( Fig. 10C View Fig 1 View Fig , H 3 View Fig ). The dorsal side lacks pseudoplicae on all but the largest specimen, where they are formed by lateral irregularly spaced series of weakly developed pustules ( Fig. 10E View Fig 1 View Fig , E 2 View Fig ). In one small specimen, the dorsal side lacks any plication and forms a single evenly convex field ( Fig. 10B View Fig ).

Remarks.—Specimens of Kennardiidae indet. from the Shackleton Limestone of the Holyoake Range have a mosaic of kennardiid features. They are united by wall-like comarginal ribs on their growth sets similar to those found in Kennardia ( Laurie 1986: fig. 7). They also fit the diagnostic criteria for Kennardiidae in having three distinct sclerite types with ubiquitous growth sets, but potentially have two symmetrical forms instead of one. No reticulate micro-ornamentation is present on the sclerites, but this is similar to other specimens recovered from the same samples (e.g., Dailyatia odyssei from samples M84.1, M84.2, recovered by Evans and Rowell 1990, see Fig. 1 View Fig ), and hence may be preservational.

Evans and Rowell (1990: 699, figs. 7.9–7.12) described specimens of Kennardiidae indet. from the same localities and referred them to two species in open nomenclature: “ Kennardia sp. A ” and “ Kennardia sp. B ” on the basis of the coarse concentric ribs similar to those in Kennardia . “ Kennardia sp. B ” was considered by Skovsted et al. (2015: 22, 31) to potentially represent Dailyatia ajax C1 sclerites, as they share a tall, conical shape, triangular transverse section with well-developed radial plicae and comarginal ribs. Evans and Rowell’s (1990) specimens were split into two species based on “ Kennardia sp. B ” being much larger and with pustules forming pseudoplicae. These criteria are not sufficient to delineate these species based on the limited number of sclerites originally described. Size is unsuitable in this case as it can be a product of different ontogenetic stages and ornamentation of kennardiid sclerites is variable within and across sclerite types.

The symmetrical first sclerite form of Kennardiidae indet. is similar to the symmetrical Form A of the monospecific genus Kennardia Laurie, 1986 , which was described from the Todd River Dolostone of the Amadeus Basin, Northern Territory, Australia ( Laurie 1986: fig. 8A). They can be clearly delineated by the lack of reticulate micro-ornament on Kennardidae indet., which is a ubiquitous character of Kennardia , along with the more strongly developed comarginal ribs ( Laurie 1986: fig. 8F–H). There may be a difference in transverse section, with the single symmetrical Kennardiidae sclerite more triangular at the apex and subcircular towards the base, and Kennardia Form A sclerites described as subrectangular ( Laurie 1986: 439), although this is not figured clearly by Laurie (1986) and based on a single sclerite of Kennardiidae indet. An A sclerite of Kennardia sp. from the Mt Scott Range of South Australia (Skovsted et al. 2015: fig. 8) is also similar to the first sclerite form of Kennardiidae indet. The dorsal side of this sclerite is also gently curved laterally with no clear delineation from the lateral fields and the apex overhangs the posterior field (Skovsted et al. 2015: fig. 8A, B). The posterior field is concave in Kennardia sp. , whereas it is flat in Kennardiidae indet.

The symmetrical second sclerite type is similar to the symmetrical sclerite of Tommotiid gen. et sp. nov. from the Koolywurtie Limestone Member of the Parara Limestone of the Stansbury Basin, South Australia (Paterson et al. 2007: fig. 4A–C). This sclerite is also tall and conical and has the same hexagonal transverse section. However, the symmetrical sclerite of Tommotiid gen. et sp. nov. is slightly curved over the ventral field, unlike Kennardiidae indet. and the comarginal ribs curve towards the apex on the lateral fields of Tommotiid gen. et sp. nov., whereas they are straight in Kennardiidae indet.

Radial plicae have been considered as a diagnostic character of Dailyatia (Skovsted et al. 2015: 18) and are also present on the ventral surface of the third, symmetrical sclerite type of Kennardiidae indet. These sclerites of Kennardiidae indet. are similar to C sclerites of some forms of Dailyatia , for example the C1 sclerites of Dailyatia ajax . The C1 sclerites of D. ajax in particular have a similar tall and pyramidal form to the third sclerite type of Kennardiidae indet. ( Fig. 10C View Fig 1 View Fig , C 2 View Fig , F 3 View Fig , H, I 1 View Fig ; Skovsted et al. 2015: fig. 16L–Q). However, the dorsal side of the C1 sclerite of D. ajax has plicae (Skovsted et al. 2015: fig. 16L–Q), a feature which is only present on the ventral side of Kennardiidae indet. ( Fig. 10C View Fig 2 View Fig , E 4 View Fig , F 1, H 1 View Fig ). Plicae are also present on the dorsal side of C2 sclerites of D. ajax Skovsted et al. 2015 : figs. 10N, 17Q).

Kennardiidae indet. can be excluded from both Kennardia and Dailyatia as it has two symmetrical sclerite types and single asymmetrical type, in contrast to a single symmetrical sclerite type and two asymmetrical types in Kennardia and Dailyatia . They can also be distinguished from Kennardia as Kennardiidae indet. has radial plicae, a feature which is diagnostic of Dailyatia . The wall-like ribs present on Kennardiidae indet. are similar to the wall-like ribs of Canadiella (Skovsted et al. 2020: figs. 5, 6), but lacks the pustulose ornamentation of this genus (Skovsted et al. 2020: figs. 5M, 6M, N)