Lanea carlsi ( Boersma, 1973 )

Slavík, Ladislav, 2011, Lanea carlsi conodont apparatus reconstruction and its significance for subdivision of the Lochkovian, Acta Palaeontologica Polonica 56 (2), pp. 313-327 : 321-325

Lanea carlsi ( Boersma, 1973)

Figs. 3–8 .

1958 Spathognathodus steinhornensis Ziegler ; Bischoff and Sannemann 1958: 106, pl. 13: 3, 7, 9.

1969 Spathognathodus cf. asymmetricus Bischoff and Sannemann ; Carls and Gandl 1969: 197, pl. 19: 1.

1973 Spathognathodus carlsi sp. nov.; Boersma 1973: 289–290, pls. 3: 1–6, 4: 1–9.

1980 Ozarkodina masara Murphy, Matti, and Walliser, 1981 (beta morphotype); Schönlaub 1980: pls. 2: 10, 16, 17; 3: 24–30; 7: 3.

1980 Ozarkodina masara Murphy, Matti, and Walliser, 1981 (beta morphotype); Chlupáč et al. 1980: pl. 20: 15–20.

?1983 Ancyrodelloides omus sp. nov. – A. transitans ; Murphy and Matti 1983 (imprint 1982): pl. 2: 13, 15, 17.

1994 Ozarkodina carlsi (Boersma) ; Valenzuela−Ríos 1994: pls. 1: 19; 3: 3, 9, 10, 14.

2007 Ozarkodina masara Schönlaub ; Boncheva et al. 2007: fig. 5L.

Material.— 12 Pa, 7 Pb, 5 M, 5 Sa, 4 Sb, 7 Sc, and 28 fragments of diverse elements were obtained from sample 4Po22; 2 Pa elements from sample 4Po32 (both samples are from Požár−3 section, Požáry Quarries near Řeporyje, Czech Republic). All figured and supplementary specimens (40 specimens) are catalogued and deposited in the National Museum Prague, Czech Republic under catalogue numbers: NM L40532–40571. All figured specimens are from sample 4 Po 22 .

Pa element (diagnostic)

Fig. 3 .

Original diagnosis.—A species of Spathognathodus with broadly flaring lips of the basal cavity. The inner lip is rounded and unornamented in upper view. The outer lip is slender, ornamented at the upper side with 1–3 thick denticles, and roughly perpendicular to the blade (from Boersma 1973).

Emended diagnosis.—A species of Lanea with weakly developed terraces on basal platform lobes. The basal cavity is shallow, strongly asymmetrical and unrestricted. The outer platform lobe is considerably larger than the inner one and its upper side is ornamented with 1 to 3 nodes interconnected with the cusp by a faint ridge.

Description.—The emended diagnosis has been added in or− der to refine the distinction by listing few more clearly observable characters of this taxon of Lanea . Boersma (1973) provided a very precise description of Pa elements in his material from Bahent locality. An even more detailed description of the material from the same area was later made by Valenzuela−Ríos (1994). Even though these descriptions are exhaustive, just a few observations of the material from the Požáry Quarries are given in this chapter using terminology which complies with the Lanea nomenclature of Murphy and Valenzuela−Ríos (1999: text−fig. 2).

The blade is often distinctly inclined at the posterior end, both in juvenile and adult specimens. The entire length of the Pa element (the main axis) varies from 0.4 mm in juvenile specimens up to 1.3 mm in adult specimens. The posterior part of the blade is much shorter than the anterior part and forms approximately 1/3 of the whole unit. Denticles on the blade are lenticular in cross section, stout or even triangular or palisade in lateral view; they are closely arranged, usually not too deeply inserted into the blade. The number of denticles depends on the ontogeny but mostly fluctuates from 12 to 17. The anterior 2–4 denticles are higher than the ones in the middle part of the blade and form an incipient fan−structure. The cusp located right above the basal pit is not always distinct; the denticles on the anterior blade between cusp and fan (cockscomb) are markedly smaller and irregular in size. The basal cavity is completely open and shallow, anterior basal groove is opened along the entire length of the anterior blade, it is deep, narrow and appressed close to anterior end. Posterior basal groove is also opened, and like in L. omoalpha tapers to the posteriormost point of the blade. It is medium deep, but gradually shallows towards the posterior end. The platform lobes are strongly asymmetrical; the outer lobe is larger than the inner lobe, sub−quadrate to round and expanded perpendicularly to the blade or slightly to the ante−

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rior. Brim and terrace are distinctly developed, the angle between the surface of the terrace and the brim is obtuse. The brim is narrower than the terrace as in other early Lanea species, brim sulcus is not developed. The terrace occupies less than 50% of platform lobe area and is equipped with 1–3 denticles which are elliptical to oval in cross−section. They are interconnected by a faint ridge that connects this ornamentation with cusp. In adult specimens these denticles are the same height as the cusp. The inner platform lobe is smaller, semicircular, unornamented and terraced. The terrace occupies usually 30% of the area of the inner lobe.

Remarks.—The above described characters of the platform element of L. carlsi point to a great similarity with Lanea omoalpha , from which differs practically only by the presence of ornamentation on one platform lobe and by increased irregularity of the lobes. The other slight differences (e.g., inclination of posterior blade, variation in denticulation and size of platform lobes) are relatively so inconspicuous that would be ordinarily regarded as variability (which is relatively high) in Lanea omoalpha . Degree of similarity in these taxa is probably at the same level or even higher than in some coeval taxa of Ancyrodelloides (e.g., A. kutscheri versus A. transitans ). L. carlsi differs from its possible immediate successor— L. omus beta by stronger inclination of posterior blade, increased asymmetry of platform lobes and by absence of denticulation of inner lateral lobe in all cases.

Pb element

Fig. 4 .

These pectiniform elements resemble to Pb elements of Zieglerodina figured by Murphy et al. (2004: figs. 2−42, 3−29). The entire unit in lower view is often S−shaped and slender. Both anterior and posterior branches are slender, of compressed lenticular shape in cross−section without any development of ledges below denticles. Although denticulation show variability, in adult specimens the number of needle−like denticles is relatively high (up to 18 on the posterior blade, up to 15 on the anterior blade). The denticles in the anterior are normally seemingly larger and less numerous than the posterior ones. The cusp is robust, stout and deeply inserted to the blade and strongly inclined posteriorly. The angle between the line segment connecting extreme points at the lower margin with axis of the cusp is up to 50°. The blade is very high from lateral view. Denticles including their insertion into the blade form usually around 1/3 of the total height of the blade in the middle areas of the anterior and posterior blade. This character differs from Pb of Zieglerodina , where this proportion is different—denticles are much higher, reaching half of total height of branch or even more. The pinch zone close to the lower margin is very high and may extend up to 1/3 of the total height of the posterior blade. The lower margin is regularly curved in lateral view. Basal cavity is small (approximately 1/5 of the entire lower margin length) and shallow.

Specimens of possible Ancyrodelloides apparatus were found in several samples in the section Požár−3, from 52 m to 69 m above the base of the section. In this interval, no Pa elements of Lanea were found, but A. transitans abounds at the 52 m. The Pb elements from this level strongly differ from the ones of L. carlsi : they have extremely inflated blades forming wide benches of the platform in upper view. They may almost reach the proportion of the platform in some Pa elements of A. transitans , where denticles occupy less than one third of the entire platform surface. The platform lobe of almost triangular shape protrudes in inner side and is slightly directed anteriorly (at angle around 80 °). The whole unit is slightly curved and the inflated blades are wider than higher (irrespective denticles) and oval to sub−angulate in cross−section. In lateral view, denticles are in general higher than the remaining basal part. The basal cavity is deep and larger than in Lanea carlsi . Similar Pb elements figured Lane and Ormiston (1979: pl. 1: 47) from Salmontrout (Alaska) and Murphy and Matti (1983: pl. 3: 21–24) from Nevada. These specimens in samples co−occur with Pa elements of A. transitans , A. kutscheri , A. trigonicus , and L. eleanorae . Although the apparatus of Ancyrodelloides has not yet been completely reconstructed, these specimens most probably belong to its apparatus. The specimens from Požár−3 section that probably belong to A. transitans differ from those mentioned above by having more inflated blade (wider benches) and larger lateral lobe. The Pb elements figured by Murphy and Matti (1983: pl. 4: 1–3) probably belong to late members of Lanea ( L. eleanorae ); they differ from the assumed Pb elements of A. transitans from the Požár−3 section by having more symmetrical basal cavity, two equal lateral lobes and less developed benches that are in much lower position below denticles in lateral view.

Sa element

Fig. 5 .

The two specimens figured ( Fig. 5A, B ) are typical representatives of the Sa element of L. carlsi in the material. The branches are relatively low with denticles alternating in size and form an angle of 110–120 °. The cusp is stout and triangular close to tip in cross section. The basal cavity below the cusp is small and shallow; it slightly ascends along the cusp and passing into faint ridge that continues along the inner side of the cusp. In outer side, the basal area of the cusp is concave.

The specimens are superficially a little similar to those of Zieglerodina sp. figured by Murphy et al. (2004: fig. 3: 30,

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(at 52 m) with possible Ancyrodelloides transitans apparatus were found distinctly different Sa elements from L. carlsi . The angle between the branches ranges 90–100 °, the basal cavity is deeper and shortly extends laterally into appressed grooves that are closed near the basal cavity. In inner view the basal cavity does not ascend along the cusp which is strongly projected out from the blade towards the inner side in upper view. In lateral view it seems to be somehow separated from the blade. In outer lateral view, the basal area of the cusp is flat. The blades are markedly inflated, not flat like in L. carlsi .

31), but the specimens of L. carlsi are more robust and the angle between branches is markedly more obtuse. In the sample

Sb element

Fig. 6 .

Although the figured elements ( Fig. 6 ) have broken denticles, in general the anterior branch shows higher irregularity in denticle size than the posterior branch which bears three big and strongly posteriorly inclined denticles forming a fanstructure. The branches are relatively low and flat, they form an angle 140–150 ° in lateral view; in upper view the extreme parts of processes are deflected inward. The basal cavity is deep, rounded to sub−rectangular in lower view, no open grooves are developed. The basal part of the cusp from outer lateral view is slightly concave; the cusp is semicircular in cross section (cf. Fig. 6A 1 ).

At the level 55 m above the base of Požár−3 section several incomplete Sb elements were found in association with A. transitans and Wurmiella . The Sb elements have many identical characters with the other transition series elements of A. transitans mentioned above (e.g., inflated blade and sharper angle between the processes). Due to breakage and scarcity of material, it is not possible to generalize other characteristics, but the difference from the Sb elements of L. carlsi is evident.

Sc element

Fig. 7 .

The Sc elements are probably twice as long as Pa elements, they are strongly curved in upper view; both processes are forming an angle of 140°. The branches are medium high in lateral view. The posterior branch bears bigger number (up to 30) of denticles, strongly alternating in size, than the anterior branch (up to 15 denticles). The anterior−most 3 or 4 denticles at the end of the anterior blade form a fan. The lower margin in lateral view is straight; the posterior branch may be slightly undulated. Branches are flat and thin as in other ramiform elements of the L. carlsi apparatus, without inflations or ledges below denticles. The cusp is strongly inclined posteriorly and slightly curved backwards, semicircular to circular in cross section; it is somewhat stepping out from array of denticles (see the detail on Fig. 7B 2 ).

The general habitus is very close to Sc element of Zieglerodina (cf. Murphy et al. 2004: fig. 3−40) but variation in denticle sizes is more irregular, not reaching rhythmicity or more regular alternation of denticle sizes like in typical Zieglerodina . The only two badly preserved Sc elements found in the sample from the level 60 m above the base of the Požár−3 section (in association with only Pa elements of A. transitans ) show conspicuous inflation of the blade which has also lower profile in lateral view.

M element

Fig. 8 .

The M elements of L. carlsi are characterized by irregular denticulation and by development of stout cusp which is semicircular to sub−triangular in cross section. The cusp bears a faint ridge in area close to the basal cavity in inner lateral view (see Fig. 8 ). This ridge may form a sharp edge of the cusp. The cusp does not terminate at the anterior of the element, but is accompanied by 1 to 3 denticles that form incipient anterior process. The blade is medium high, flat and regularly arched. The number of denticles on the posterior process may reach 22. The basal cavity is small and almost triangular in shape.

The only one complete M element that possibly belongs to A. transitans was found at the same sample as the other mentioned ramiforms in the Požár−3 section. It strongly differs from the M element of L. carlsi by typical thickening (inflation) of the posterior process, more regular denticulation and larger and deeper basal cavity that continues shortly as a groove towards posterior. The basal cavity of this specimen is widely open below the cusp and forms small but distinctly developed lateral lobe in the inner lateral side.

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Figures

Fig. 3. SEM photographs of Pa elements of spathognathodontid conodont Lanea carlsi (Boersma, 1973). A. NM L40532, upper view (A1), detail of the platform lobe denticulation (A2), the terrace on platform lobe with single node connected by ridge with cusp. B. NM L40533, upper view (B1), detail of the cusp and neighboring denticle (B2). C. NM L40534, upper view (C1), detail of the ornamentation of the outer platform lobe (C2). All figured specimens are from sample 4Po22.

Fig. 4. SEM photographs of Pb elements of spathognathodontid conodont Lanea carlsi (Boersma, 1973). A. NM L40535, incomplete element, inner lateral view (A1), detail of the basal area (A2). B. NM L40536, adult element, outer lateral view (B1), detail of denticles on posterior blade (B2). C. NM L40537, detail of denticulation on posterior blade (C1), outer lateral view (C2). All figured specimens are from sample 4Po22.

Fig. 5. SEM photographs of Sa elements of spathognathodontid conodont Lanea carlsi (Boersma, 1973). A. NM L40540, complete element, anterior view (A1), detail of cusp area (A2). B. NM L40541, posterior view (B1), detail of basal cavity (B2). All figured specimens are from sample 4Po22.

Fig. 6. SEM photographs of Sb elements of spathognathodontid conodont Lanea carlsi (Boersma, 1973). A. NM L40542, detail of cusp in cross section (A1), detail of basal cavity (A2), inner lateral view (A3). B. NM L40543, outer lateral view (B1), detail of basal area (B2). All figured specimens are from sample 4Po22.

Fig. 7. SEM photographs of Sc elements of spathognathodontid conodont Lanea carlsi (Boersma, 1973). A. NM L40544, inner lateral view (A1), detail of basal cavity (A2). B. NM L40545, outer lateral view (B1), detail of cusp area (B2). All figured specimens are from sample 4Po22.

Fig. 8. SEM photographs of M elements of spathognathodontid conodont Lanea carlsi (Boersma, 1973). A. NM L40538, incomplete element, inner lateral view (A1) detail of broken cusp (A2). B. NM L40539, inner lateral view (B1), detail of basal area with ridge (B2). All figured specimens are from sample 4Po22.

Fig. 1. A. Map with marked ocurrences of Lanea carlsi in Europe: 1, Eastern Iberian Chains; 2, Spanish Central Pyrenees; 3, Frankenwald; 4, Prague Synform (Barrandian); 5, Carnic Alps; 6, Western Bulgaria. B. Location of the Požáry Quarries in the Prague Synform (Barrandian, Czech Republic).

Fig. 2. Stratigraphy of the lower and middle part of the Požár−3 section with ranges of stratigraphically most important cosmopolitan conodonts in relation with the range of Lanea carlsi. The samples are marked on the right side of the column. The sample numbers are marked on the right side of the column. For convenience the sample prefix (4Po) is omitted. The samples with other prefixes (from different samplings and re−samplings) are given in full (i.e., PZ14, PZ16, and R52.0).