Baculites

Baculites; Temporal range:96–65Ma PreꞒ Ꞓ O S D C P T J K Pg N UpperCretaceousto LowerPaleocene
	Baculitesfossils from South Dakota. Some still have traces of the originalnacre(shells).
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	†Ammonoidea
Order:	†Ammonitida
Suborder:	†Ancyloceratina
Family:	†Baculitidae
Genus:	†Baculites; Lamarck,1799
Type species
	†Baculites vertebralis; Lamarck, 1801vide Meek, 1876
Species
	See text

Baculitesis an extinct genus of heteromorphammonite cephalopodswith almost straight shells. The genus, which lived worldwide throughout most of theLate Cretaceous,and which brieflysurvivedtheK-Pg mass extinction event,was named byLamarckin 1799.^[3]^[4]

Life

Shell anatomy

The adult shell ofBaculitesis generally straight and may be either smooth or with sinuous striae or ribbing that typically slant dorso-ventrally forward. The aperture likewise slopes to the front and has a sinuous margin. The venter is narrowly rounded to acute while the dorsum is more broad. The juvenile shell, found at the apex, is coiled in one or two whorls and described as minute, about 1 centimetre (0.39 in) in diameter. AdultBaculitesranged in size from about 7 centimetres (2.8 in) (Baculites larsoni) up to 2 metres (6.6 ft) in length.

As with otherammonites,the shell consisted of a series of camerae, or chambers, that were connected to the animal by a narrow tube called a siphuncle by which gas content and thereby buoyancy could be regulated in the same manner asNautilusdoes today. The chambers are separated by walls called septa. The line where each septum meets the outer shell is called the suture or suture line. Like other trueammonites,Baculiteshave intricate suture patterns on their shells that can be used to identify different species.

One notable feature aboutBaculitesis that the males may have been a third to a half the size of the females and may have had much lighter ribbing on the surface of the shell.

Orientation

The shell morphology ofBaculiteswith slanted striations or ribbing, similarly slanted aperture, and more narrowly rounded to acute keel-like venter points to its having had a horizontal orientation in life as an adult. This same type of cross section is found in much earliernautiloidssuch asBasslerocerasandClitendocerasfrom theOrdovicianperiod, which can be shown to have had a horizontal orientation. In spite of this, some researchers have concluded that Baculites lived in a vertical orientation, head hanging straight down, since lacking an apical counterweight, movement was largely restricted to that direction. More recent research, notably by Gerd Westermann, has reaffirmed that at least someBaculitesspecies in fact lived in a more or less horizontal orientation.^[5]

Ecology

From shell isotope studies, it is thought thatBaculitesinhabited the middle part of the water column, not too close to either the bottom or surface of the ocean. In some rock depositsBaculitesare common, and they are thought to have lived in great shoals. However, they are not known to occur so densely as to be rock-forming, as do certain other extinct, straight-shelled cephalopods (e.g.,orthocerid nautiloids). Studies on exceptionally preserved specimens have revealed aradulabysynchrotronimagery.^[6]The results suggest thatBaculitesfed on pelagiczooplankton(as suggested by remains of a larvalgastropodand a pelagicisopodinside the mouth).^[7]

Convergent evolution

Baculitesand relatedCretaceousstraightammonitecephalopods are often confused with the superficially similarorthocerid nautiloidcephalopods. Both are long and tubular in form, and both are common items for sale in rock shops (often under each other's names). Both lineages evidently evolved the tubular form independently, and at different times in earth history. Theorthocerid nautiloidsmostly lived much earlier (common during thePaleozoicEra, possibly going extinct in theEarly Cretaceous)^[8]thanBaculites(LateCretaceous-Danianonly). The two types of fossils can be distinguished by many features, most obvious among which is the suture line: it is simple in orthocerid nautiloids and intricately folded inBaculitesand related ammonoids.

Species distribution

*Baculites*specimen in the field; western South Dakota,Pierre Shale,Late Cretaceous. Part of the phragmocone (left) and part of the body chamber (right) are present.

*Baculites*showing sutures and remnantaragonite;western South Dakota, Late Cretaceous.

*Baculites*from the Late Cretaceous of Wyoming. The original aragonite of the outer conch and inner septa has dissolved away, leaving this articulated internal mold.

Cenomanian:

Baculites gracilisis known from the CenomanianBritton Formation.

Turonian:

Baculites undulatus,from the upper Turonian of Europe.^[9]

Campanian:

The lower part of the Campanian stage (Upper Cretaceous) in the Western Interior of North America has yieldedBaculites gilberti,earlyB. perplexus,B. asperiformis,B. maclearni,andB. obtusus,followed temporally by lateBaculites perplexusand then byBaculites scotti.The upper part of the upper Campanian has yielded, from older to younger,B. compressus,B. coneatus,B. reesidei.B. jenseni,andB. ellasi,followed sequentially in the lower Maastrictian byBaculites baculus,B. grandis,andB. clinolobatis.^[10]^[11]

Baculites pacificumis known from the Campanian of Vancouver Island, British Columbia, andBaculites leopoliensisfrom the Upper Campanian of Europe.^[12]

Maastrichtian/Danian:

The type species,Baculites vertebralisis from the upper Maastrichtian and Danian, and is one of thevery last species of ammonites.Findings in Denmark and the Netherlands suggest the species survived theK-Pg mass extinction event,albeit being restricted to theDanian.^[3]^[13]^[14]Baculites ancepsis also known from Europe, although only from the Upper Maastrichtian.^[12]

Baculites ovatusis known from the Maastrichtian deposits ofRipley FormationinMcNairy County, Tennessee,andSevern FormationinPrince George's County, Maryland.^[15]

Cultural significance

Baculitesfossils are very brittle and almost always break. They are most commonly found broken in half or several pieces, usually along suture lines. Individual chambers found this way are sometimes referred to as "stone buffaloes" (due to their shapes), though the Native-American attribution typically given as part of the story behind the name is likely apocryphal.^{[clarification needed]}The Blackfoot have oral traditions that tell a story of the Iniskimm (Buffalo Calling Stone). They are still in use today by Indigenous peoples.

Baculites ovatus,the first species ofBaculitesdescribed in the Americas, was described byThomas Sayin 1820^[16]from a single specimen from theNavesink FormationinAtlantic Highlands, New Jersey.The specimen was later illustrated bySamuel George Morton,who published an etching in 1828.^[17]After the death of the specimen's owner, the Quaker scientistReuben Haines III,in 1831, the specimen was lost for 180 years until it was rediscovered at Haines's home, the historicWyck House,in 2017 by Matthew Halley.^[18]

References

^Lamarck, J. P. B. A. de M. de (1801):Systeme des Animaux sans vertebres.The author; Deterville, Paris, vii + 432 pp.
^Meek, F. B. (1876): A report on the invertebrate Cretaceous and Tertiary fossils of the upper Missouri country. In Hayden,F. V.Report of the United States Geological Survey of the Territories,9, lxiv + 629 pp., 45 pis
^^a ^bLandman, Neil H.; Goolaerts, Stijn; Jagt, John W.M.; Jagt-Yazykova, Elena A.; Machalski, Marcin (2015), Klug, Christian; Korn, Dieter; De Baets, Kenneth; Kruta, Isabelle (eds.),"Ammonites on the Brink of Extinction: Diversity, Abundance, and Ecology of the Order Ammonoidea at the Cretaceous/Paleogene (K/Pg) Boundary",Ammonoid Paleobiology: From macroevolution to paleogeography,Topics in Geobiology, Dordrecht: Springer Netherlands, pp. 497–553,doi:10.1007/978-94-017-9633-0_19,ISBN 978-94-017-9633-0,retrieved2024-02-13
^Lamarck, J. P. B. A. de M. de (1799): Prodrome d'une nouvelle classification des coquilles.Mem. Soc. Hist. Nat.Paris,(1799), 63-90.
^Westermann, G. E. G. (1996). Ammonoid life and habitat. In N. H. Landman, K. Tanabe, and R. A. Davis (editors),Ammonoid Paleobiology,pp. 607–707. New York: Plenum Press.
^Kruta, I.; Landman, N.; Rouget, I.; Cecca, F.; Tafforeau, P. (2011). "The Role of Ammonites in the Mesozoic Marine Food Web Revealed by Jaw Preservation".Science.331(6013): 70–72.Bibcode:2011Sci...331...70K.doi:10.1126/science.1198793.PMID 21212354.S2CID 206530342.
^Neil H. Landman, Richard Arnold Davis, Royal H. Mapes (2007).Cephalopods. Present and Past: New Insights and Fresh Perspectives. Chapter 13: Jaws and Radula ofBaculitesfrom the Upper Cretaceous (Campanian) of North America(PDF).Springer. pp. 257–298.ISBN 978-1-4020-6806-5.Archived fromthe original(PDF)on September 12, 2013.{{cite book}}:CS1 maint: multiple names: authors list (link)
^Doguzhaeva, Larisa (1994-01-01)."An Early Cretaceous orthocerid cephalopod from North-Western Caucasus".Palaeontology.37:889–899.
^"Baculites undulatusd'Orbigny, 1847 ".crioceratites.free.fr.Archivedfrom the original on February 13, 2024.Retrieved2024-02-13.
^"Ammonite Zones (International Stratigraphy Standards)".North American Research Group.Archivedfrom the original on October 4, 2023.
^"Baculitidae (Gill 1871)".Jdsamonites.Archivedfrom the original on June 5, 2023.
^^a ^b"Baculitidae GILL 1871".www.ammonites.fr.Archived fromthe originalon May 27, 2022.
^"Bulletin Volume 52 – 2005".Dansk Geologisk Forening(in Danish). 2005-05-25.doi:10.37570/bgsd-2005-52-08.Retrieved2024-02-13.
^W. M. Jagt, John (2012-01-01)."Ammonieten uit het Laat-Krijt en Vroeg-Paleogeen van Limburg".Grondboor & Hamer.66(1): 154–183.
^"Mesozoic_Cephalopods".earthphysicsteaching.homestead.com.Archivedfrom the original on September 22, 2023.Retrieved2024-02-13.
^Say, Thomas (1820)."Observations on some species of Zoophytes, Shells, &c. principally fossil (part 2)".The American Journal of Science and Arts.2:34–45.
^Morton, Samuel George (1828)."Description of the fossil shells which characterize the Atlantic Secondary Formation of New Jersey and Delaware; including four new species".Journal of the Academy of Natural Sciences of Philadelphia.6:72–90.
^Halley, Matthew R. (2019)."Rediscovery of the holotype of the extinct cephalopod Baculites ovatus Say, 1820 after nearly two centuries".Proceedings of the Academy of Natural Sciences of Philadelphia.167(1): 1–9.doi:10.1635/053.167.0101.ISSN 0097-3157.S2CID 164642352.