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Hornerstown Formation

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Hornerstown Formation
Stratigraphic range: latest Maastrichtian-early Danian[1]
66.5–65.5 Ma
↓
TypeGeological formation
UnderliesVincentown Formation
OverliesNew Egypt Formation, Navesink Formation and Tinton Formation
Location
RegionNew Jersey
CountryUSA

The Hornerstown Formation is a latest Cretaceous to earliest Paleocene-aged geologic formation in New Jersey. It preserves a variety of fossil remains, including those of dinosaurs, and contains direct evidence of the mass mortality that occurred at the Cretaceous-Paleogene boundary.[2][3]

Outcrops of the Hornerstown Formation are known from sites such as Edelman Fossil Park.[4]

Age & significance

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The age of the Hornerstown deposits have been controversial. While most fossils are of animal taxa known from the earliest Cenozoic era, several fossils of otherwise exclusively Cretaceous age have been found. These include remains of the shark Squalicorax, several types of non-avian dinosaurs, the teleost fish Enchodus, several species of ammonite, and marine lizards referred to the genus Mosasaurus. Some of these remains show signs of severe abrasion and erosion, however, implying that they may be re-worked from older deposits. Most of these fossils are restricted to the lowest point in the formation, one rich in fossils and known as the Main Fossiliferous Layer, or MFL. Other explanations for the out-of-place fossils in the MFL is that they represent a time-averaged assemblage that built up and remained unburied during a time of low sediment deposition, or that they were stirred up from deeper in the sediment and deposited together during a tsunami.[5] Biochemical analyses done on mosasaur bones from the Hornerstown Formation and the underlying, purely Cretaceous New Egypt Formation have found differing chemical signatures in the content of rare earth elements depending on whether the bones derive from the New Egypt or the Hornerstown Formation. This provides evidence against the idea that the presence of these remains in the Hornerstown is just the result of reworking, and supports the Hornerstown Formation including Cretaceous strata.[6]

To account for these Cretaceous fossils, the Hornerstown Formation is generally treated as including the last portion of the Maastrichtian shortly before the Cretaceous-Paleogene boundary, and is thus divided into three sections: the section below the MFL (entirely Maastrichtian), the MFL itself (at the K-Pg boundary), and the section above the MFL (entirely Danian). However, other studies continue to treat the Hornerstown Formation as a Paleocene formation that saw significant reworking of Cretaceous fossils into itself.[7] In addition, recent studies have found evidence of high iridium concentration and shocked quartz within the MFL, suggesting that the MFL represents a thanatocoenosis formed from an ecosystem collapse during the Cretaceous-Paleogene extinction event. This makes the Hornerstown Formation one of the few geological formations to contain direct evidence of the immediate impact of the extinction event. The Hornerstown Formation is important paleontologically, as it shows the impact of the K-Pg extinction on the coastal waters of eastern Appalachia, contains many of the last known records of taxa that went extinct at the K-Pg boundary, while also providing evidence of survivorship for the taxa that managed to survive the extinction event.[3]

Vertebrate paleofauna

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Ray-finned fishes

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Actinopterygii of the Hornerstown Formation
Genus Species Location Stratigraphic position Abundance Material Notes Images
Acipenser A. cf. albertensis Maastrichtian A sturgeon.[3]
Anomoeodus A. phaseolus Maastrichtian, potentiallyDanian 8 teeth A pycnodont. One tooth is known from the Danian section of the formation, which would be the latest record of this genus and prove its occurrence in the Cenozoic; however, it may have been reworked from lower layers.[3]
Atractosteus A. sp. Maastrichtian & Danian 11 teeth A gar. First record of gars from eastern North America during the Paleocene.[3]
cf. Bananogmius cf. B. sp. Maastrichtian A plethodid tselfatiiform.[3]
Dercetidae indet. Maastrichtian & Danian 27 flank scales A dercetid aulopiform. The first evidence in eastern North America of the Dercetidae surviving the K-Pg extinction event.[3]
Enchodus E. ferox Maastrichtian An enchodontid aulopiform. The E. gladiolus remains are the first record of the species in eastern North America.[3]
E. gladiolus 8 teeth
Iridopristis I. parrisi Sewell, New Jersey Danian 3 partial articulated specimens, including a near-complete skull.[7] A stem-lineage member of Holocentridae. The earliest known definitive holocentrid.[7]
Paralbula P. marylandica Maastrichtian & Danian 23 teeth A phyllodontid elopomorph. First evidence of P. marylandica existing during the Cretaceous, indicating that it survived the extinction event.[3]
Phyllodus P. paulkatoi Maastrichtian 1 tooth plate A phyllodontid elopomorph. First known occurrence in eastern North America.[3]
Saurocephalus S. lanciformis Danian 1 tooth A saurodontid ichthyodectiform. First known occurrence in eastern North America and first known occurrence of ichthyodectiforms as a whole in the Paleocene and Cenozoic.[3]

Reptiles

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Birds

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Birds of the Hornerstown Formation
Genus Species Location Stratigraphic position Abundance Notes

Anatalavis[8]

A. rex.[8]

Graculavus[8]

G. velox[8]

Laornis[8]

L. edwardsianus[8]

Palaeotringa[8]

P. littoralis[8]

P. vagans[8]

Telmatornis[8]

T. priscus[8]

Tytthostonyx[8]

T. glauconiticus[8]

Non-avian dinosaurs

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Dinosaurs of the Hornerstown Formation
Genus Species Location Stratigraphic position Abundance Notes
Hadrosauridae indet. Maastrichtian A hadrosaurid ornithischian.[3]

The tyrannosauroid Dryptosaurus is sometimes referred to this formation, as its remains were found in the New Egypt Formation, which is sometimes considered a part of the Hornerstown.[9]

Crocodylomorphs

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Crocodylomorphs of the Hornerstown Formation
Genus Species Location Stratigraphic position Abundance Notes

Bottosaurus[10]

B. harlani

Hyposaurus[11] H. rogersii

Turtles

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Testudines of the Hornerstown Formation
Genus Species Location Stratigraphic position Abundance Notes

Osteopygis[1]

O. emarginatus

Maastrichtian-Danian
Euclastes E. wielandi found as a separate genus from the cranial material of Osteopygis

Mosasaurs

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Mosasaurs of the Hornerstown Formation
Genus Species Location Stratigraphic position Abundance Material Notes Images
Mosasaurus M. hoffmanni Maastrichtian Pterygoid, teeth, vertebrae[3][6] A mosasaurine. This formation contains some of the last known remains, comprising individuals killed during the mass mortality event that formed the MFL.[3] A very large specimen is known.[6]
Plioplatecarpus P. sp. Maastrichtian A plioplatecarpine.

See also

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References

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  1. ^ a b Gentry, A.D.; Kiernan, C.R.; Parham, J.F. (2022). "A large non-marine turtle from the Upper Cretaceous of Alabama and a review of North American "Macrobaenids"". The Anatomical Record. 306 (6): 1411–1430. doi:10.1002/ar.25054. PMID 37158131.
  2. ^ Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
  3. ^ a b c d e f g h i j k l m n Boles, Zachary; Ullmann, Paul; Putnam, Ian; Ford, Mariele; Deckhut, Joseph (2024-04-12). "New vertebrate microfossils expand the diversity of the chondrichthyan and actinopterygian fauna of the Maastrichtian–Danian Hornerstown Formation in New Jersey". Acta Palaeontologica Polonica. doi:10.4202/app.01117.2023.
  4. ^ Voegele, Kristyn K.; Ullmann, Paul V.; Lonsdorf, Tara; Christman, Zachary; Heierbacher, Michael; Kibelstis, Brian J.; Putnam, Ian; Boles, Zachary M.; Walsh, Shane; Lacovara, Kenneth J. (2021-11-01). "Microstratigraphic Analysis of Fossil Distribution in the Lower Hornerstown and Upper Navesink Formations at the Edelman Fossil Park, NJ". Frontiers in Earth Science. 9: 1033. Bibcode:2021FrEaS...9.1033V. doi:10.3389/feart.2021.756655. ISSN 2296-6463.
  5. ^ Gallagher, W.B. (2005). "Recent mosasaur discoveries from New Jersey and Delaware, USA: stratigraphy, taphonomy and implications for mosasaur extinction." Netherlands Journal of Geosciences — Geologie en Mijnbouw, 84(3): 241-245. [1] Archived 2012-09-04 at the Wayback Machine
  6. ^ a b c Gallagher, W. B. (2015). "Greensand mosasaurs of New Jersey and the Cretaceous–Paleogene transition of marine vertebrates". Netherlands Journal of Geosciences. 94 (1): 87–91. Bibcode:2015NJGeo..94...87G. doi:10.1017/njg.2014.30. ISSN 0016-7746.
  7. ^ a b c Andrews, J. V.; Schein, J. P.; Friedman, M. (2023). "An earliest Paleocene squirrelfish (Teleostei: Beryciformes: Holocentroidea) and its bearing on the timescale of holocentroid evolution". Journal of Systematic Palaeontology. 21 (1). Bibcode:2023JSPal..2168571A. doi:10.1080/14772019.2023.2168571.
  8. ^ a b c d e f g h i j k l m "3.22 New Jersey, United States; 7. Hornerstown Formation," in Weishampel, et al. (2004). Page 586.
  9. ^ Olsson, R.K. (1960). "Foraminifera of latest Cretaceous and earliest Tertiary age in the New Jersey coastal plain". Journal of Paleontology. 34: 1–58.
  10. ^ Cossette, A. P., and C. A. Brochu. 2018. A new specimen of the alligatoroid Bottosaurus harlani and the early history of character evolution in alligatorids. Journal of Vertebrate Paleontology. DOI:10.1080/02724634.2018.1486321.
  11. ^ Morgan, Donald J (December 2018). "PRESENCE OF A DYROSAURID NEOSUCHIAN IN THE SEVERN/BRIGHTSEAT FORMATION OF MARYLAND". The Journal of the Delaware Valley Paleontological Society. X: 91 to 104.

Bibliography

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  • Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.


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