Line of praise
In fossil ammonoids and nautiloids, lines of praise are the seams between the housing wall and the chamber partition walls (septa). The line of praise is visible on the stone cores of the fossil species immediately after removing the shell . Their shape is the most important property of the ammonite shell for differentiating the different types of ammonoids. The line of praise is mostly wavy. The curvatures running towards the mouth (front) are called saddles, the ends tapering away from the mouth (back) are called lobes. The line of praise is shown rolled up, it begins at the convex outer edge of the bowl and ends at the concave inner edge of the turn. Particularly the increasing complication of the folding of the septa of ammonites is the subject of the investigation. There are two possible interpretations:
- Septa are seen as important supporting elements for the phragmocone. The corrugated sheet-like folding of the septa should help to counteract the hydrostatic pressure directed from the outside onto the phragmocone.
- The folding of the septa benefits the diving behavior because of the increased surface area . Here, the folding of the septa is intended to accelerate the transport of the chamber fluid and enable better immersion and emergence speeds.
Distinction
A distinction is made between the following types of line of praise:
- Prosuture: the praised line of the smooth or oval initial chamber
- Primary suture: first typical line of praise of the first air chamber in the ontogenetic development of the ammonite
- Secondary suture: arises from the primary suture by increasing praise
Despite the diversity of ammonites and the formation of the praised lines, three types can be identified, which, however, do not represent a clear evolutionary sequence in geological terms. Originally, the three large groups were equated with a chronological sequence: Goniatites (Palaeoammonoidea) in the Devonian to Permian , Ceratites (Mesoammonoidea) in the Triassic and ammonites (Neoammonoidea) in the Jurassic and Cretaceous . However, this original, simple subdivision can no longer be maintained, since ceratitic and goniatitic praise lines also exist in the Chalk and ammonite praise lines also in the Permian. The new structure is based on the phylogeny of the primary suture: Devonian to Permian with a three-lobed (trilobate) primary suture (ELI, for the meaning of the abbreviations see below), Triassic with a four-lobed (quadrilobate) primary suture (ELUI) and Jurassic with a five-lobed (quinquelobate) Primary Suture (ELU2U1I). There are three different forms in chalk: quadrilobat, quinquelobat and sexlobat (six-lobed, ELU2U3U1I).
The three types of praise lines are structured according to their complexity:
- Goniatitic shape: suture curved or kinked in a wave shape; no slashing of praise
- Ceratite shape: saddles with entire margins, lobes serrated to the rear
- Ammonite form: highly branched saddles and praises
Depending on the position on the housing, different sections of the corrugations of the septum that cause the line of praise are given their own names. The praises are of particular importance for the determination of the ammonoids:
- External lobe on the outside above the keel of the housing (E)
- Adventitious lobe between the external and lateral lobes, sometimes several (A 1 , A 2 , etc.)
- Lateral lobe on the side surface, usually significantly larger than the umbilical lobe (L)
- Umbilical lobe between the lateral lobe and the internal lobe, often several (U 1 , U 2 , U 3 etc.)
- Internal lobe on the inside of the casing coil (I)
The abbreviation of the existing praise has become naturalized through the praise formula, which summarizes the praises that occur. For example, the genus Discoclymenia from Upper Devon has the praise formula EA 3 A 2 A 1 LUI.
Individual evidence
- ^ Emil Kuhn Schnyder, Hans Rieber: Palaeozoology - Morphology and systematics of extinct animals. Georg Thieme Verlag, Stuttgart / New York 1984, ISBN 3-13-653301-1 .