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Hornerstown Formation

{{Short description|Geological Formation in New Jersey}}

{{Infobox rockunit

| name = Hornerstown Formation

| image =

| caption =

| type = Geological formation

| age = latest Maastrichtian-Danian{{cite journal|author1=Gentry, A.D.|author2=Kiernan, C.R.|author3=Parham, J.F.|year=2022|title=A large non-marine turtle from the Upper Cretaceous of Alabama and a review of North American "Macrobaenids"|journal=The Anatomical Record|volume=306 |issue=6 |pages=1411–1430 |doi=10.1002/ar.25054|pmid=37158131 }}
{{fossilrange|66.5|62}}

| period = Maastrichtian

| prilithology =Marl, greensand

| otherlithology =

| namedfor =Hornerstown, New Jersey

| namedby =

| region = New Jersey

| country = United States

| coordinates =

| unitof =Rancocas Group

| subunits =

| underlies = Vincentown Formation

| overlies = New Egypt Formation, Navesink Formation and Tinton Formation

| thickness =

| extent =

| area =

| map =

| map_caption =

}}

The Hornerstown Formation is a latest Cretaceous to early 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.Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.{{Cite journal |last1=Boles |first1=Zachary |last2=Ullmann |first2=Paul |last3=Putnam |first3=Ian |last4=Ford |first4=Mariele |last5=Deckhut |first5=Joseph |date=2024-04-12 |title=New vertebrate microfossils expand the diversity of the chondrichthyan and actinopterygian fauna of the Maastrichtian–Danian Hornerstown Formation in New Jersey |url=https://rdw.rowan.edu/see_facpub/102/ |journal=Acta Palaeontologica Polonica |doi=10.4202/app.01117.2023|doi-access=free }}{{Cite journal |last=Staron |first=Richard M. |last2=Grandstaff |first2=Barbara S. |last3=Gallagher |first3=William B. |last4=Grandstaff |first4=David E. |date=2001 |title=REE Signatures in Vertebrate Fossils from Sewell, NJ: Implications for Location of the K-T Boundary |url=https://www.jstor.org/stable/3515603 |journal=PALAIOS |volume=16 |issue=3 |pages=255–265 |doi=10.2307/3515603 |issn=0883-1351|url-access=subscription }}

Outcrops of the Hornerstown Formation are known from sites such as Edelman Fossil Park.{{Cite journal |last1=Voegele |first1=Kristyn K. |last2=Ullmann |first2=Paul V. |last3=Lonsdorf |first3=Tara |last4=Christman |first4=Zachary |last5=Heierbacher |first5=Michael |last6=Kibelstis |first6=Brian J. |last7=Putnam |first7=Ian |last8=Boles |first8=Zachary M. |last9=Walsh |first9=Shane |last10=Lacovara |first10=Kenneth J. |date=2021-11-01 |title=Microstratigraphic Analysis of Fossil Distribution in the Lower Hornerstown and Upper Navesink Formations at the Edelman Fossil Park, NJ |journal=Frontiers in Earth Science |language=English |volume=9 |page=1033 |doi=10.3389/feart.2021.756655 |doi-access=free |bibcode=2021FrEaS...9.1033V |issn=2296-6463}}

Age & significance

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.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. [http://www.njgonline.nl/publish/articles/000257/article.pdf] {{Webarchive|url=https://web.archive.org/web/20120904202306/http://www.njgonline.nl/publish/articles/000257/article.pdf|date=2012-09-04}} 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.{{Cite journal |last=Gallagher |first=W. B. |date=2015 |title=Greensand mosasaurs of New Jersey and the Cretaceous–Paleogene transition of marine vertebrates |url=https://www.cambridge.org/core/journals/netherlands-journal-of-geosciences/article/greensand-mosasaurs-of-new-jersey-and-the-cretaceouspaleogene-transition-of-marine-vertebrates/60F0808E2A2A4EC08DB91CFBD5D21668 |journal=Netherlands Journal of Geosciences |language=en |volume=94 |issue=1 |pages=87–91 |doi=10.1017/njg.2014.30 |bibcode=2015NJGeo..94...87G |issn=0016-7746}}

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.{{cite journal |last1=Andrews |first1=J. V. |last2=Schein |first2=J. P. |last3=Friedman |first3=M. |year=2023 |title=An earliest Paleocene squirrelfish (Teleostei: Beryciformes: Holocentroidea) and its bearing on the timescale of holocentroid evolution |journal=Journal of Systematic Palaeontology |volume=21 |issue=1 |doi=10.1080/14772019.2023.2168571 |doi-access=free|bibcode=2023JSPal..2168571A }} 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.

Vertebrate paleofauna

= Cartilaginous fishes =

Based on Case (1996) and Boles et al (2024):{{Cite journal |last=Case |first=Gerard R. |date=1996-12-19 |title=A new Selachian Fauna from the Lower Hornerstown Formation (Early Paleocene/Montian) of Monmouth County, New Jersey |url=https://www.schweizerbart.de/papers/pala/detail/242/101028/A_new_Selachian_Fauna_from_the_Lower_Hornerstown_F?af=crossref |journal=Palaeontographica Abteilung A |volume=242 |issue=1–3 |language=en |pages=1–14 |doi=10.1127/pala/242/1996/1|bibcode=1996PalAA.242....1C |url-access=subscription }}

== Chimaeras ==

class="wikitable" align="center" width="100%"
colspan="9" align="center" |Chimaeras of the Hornerstown Formation
Genus

! Species

! Location

! Stratigraphic position

! Abundance

!Material

! Notes

!Images

rowspan="4" |Edaphodon

|E. agassizi

|

|Danian

|

| rowspan="4" |Tooth plates

| rowspan="4" |A callorhinchid chimaera.

| rowspan="4" |File:Edaphodon AMNH.jpg

E. mantelli

|

|Danian

|

E. mirificus

|

|Maastrichtian

|

E. stenobyrus

|

|Maastrichtian

|

rowspan="3" |Ischyodus

|I. bifurcatus

| rowspan="2" |

|Maastrichtian, potentially Danian

|

| rowspan="3" |Tooth plates, jaw elements

| rowspan="3" |A callorhinchid chimaera.

| rowspan="3" |frameless

I. thurmanni

|Maastrichtian

|

I. williamsae

|

|Danian

|

== Sharks ==

class="wikitable" align="center" width="100%"
colspan="9" align="center" |Sharks of the Hornerstown Formation
Genus

! Species

! Location

! Stratigraphic position

! Abundance

!Material

! Notes

!Images

Araloselachus

|A. cuspidatus

|

|Maastrichtian

|

| rowspan="21" |Teeth

|A sand shark.{{Cite web |title=PBDB Collection |url=https://paleobiodb.org/classic/basicCollectionSearch?collection_no=26819 |access-date=2024-11-12 |website=paleobiodb.org}}

|File:FOS527C.jpg

Carcharias

|C. teretidens

|

|Danian

|

|A relative of the sand tiger shark.

|frameless

Cretalamna

|C. appendiculata

|

|Maastrichtian & Danian

|

|A megatooth shark.

|frameless

Heptranchias

|H. howellii

|

|Maastrichtian

|

|A relative of the sharpnose sevengill shark.

|frameless

rowspan="2" |Hexanchus

|H. microdon

|

|Danian

|

| rowspan="2" |A sixgill shark.

| rowspan="2" |frameless

H. sp.

|

|Maastrichtian & Danian

|

Otodus

|O. obliquus

|

|Danian

|

|A megatooth shark.

|frameless

Odontaspis

|O. sp.

|

|Danian

|

|A sand shark.

|frameless

Palaeocarcharodon

|P. sp.

|

|Danian

|

|A megatooth shark.

|frameless

Palaeogaleus

|P. vincenti

|

|Maastrichtian & Danian

|

|A houndshark.

|File:Palaeogaleus faujasi.jpg

Palaeohypotodus

|P. rutoti

|

|Danian

|

|A sand shark.

|File:Palaeohypotodus bronni.jpg

Pseudocorax

|P. affinis

|

|Maastrichtian

|

|A pseudocoracid shark.

|File:Psuedocorax granti.jpg

Scapanorhynchus

|S. texanus

|

|Maastrichtian

|

|A goblin shark.{{Cite web |title=PBDB Collection |url=https://paleobiodb.org/classic/basicCollectionSearch?collection_no=124938 |access-date=2024-11-12 |website=paleobiodb.org}}

|frameless

Scyliorhinus

|S. gilberti

|

|Danian

|

|A catshark.

|frameless

Sphenodus

|S. lundgreni

|

|Maastrichtian

|

|A orthacodontid shark.

|frameless

Squalicorax

|S. pristodontus

|

|Maastrichtian

|

|A crow shark.

|frameless

rowspan="2" |Squalus

|S. minor

|

| rowspan="2" |Maastrichtian & Danian

|

| rowspan="2" |A spurdog.

| rowspan="2" |frameless

S. sp

|

|

Squatina

|S. sp.

|

|Maastrichtian

|

|An angelshark.

|frameless

Weltonia

|W. ancistrodon

|

|Danian

|

|A cow shark.

|

Xampylodon

|X. brotzeni

|

|Maastrichtian

|

|A cow shark.

|File:Notidanodon.jpg

== Rays ==

class="wikitable" align="center" width="100%"
colspan="9" align="center" |Rays of the Hornerstown Formation
Genus

! Species

! Location

! Stratigraphic position

! Abundance

!Material

! Notes

!Images

Aetomylaeus

|A. striatus

|

|Maastrichtian

|

| rowspan="8" |Teeth

|An eagle ray.

|frameless

Dasyatis

|D. crosswickense

|

|Danian

|

|A whiptail stingray. Type locality for species.

|frameless

Hypolophites

|H. hutchinsi

|

|Danian

|

|A whiptail stingray. Type locality for species.

|

Hypolophodon

|H. sylvestris

|

|Danian

|

|A whiptail stingray.

|

Ischyrhiza

|I. mira

|

|Maastrichtian

|

|A sclerorhynchid sawskate.

|frameless

Rhinoptera

|R. sp.

|

|Maastrichtian

|

|A cownose ray.

|frameless

Rhombodus

|R. laevis

|

|Maastrichtian

|

|A rhombodontid ray.

|frameless

Viperecucullus

|V. kuehnei

|

|Danian

|

|A whiptail stingray, type locality for the species and genus.

|

=Ray-finned fishes=

class="wikitable" align="center" width="100%"
colspan="9" align="center" |Actinopterygii of the Hornerstown Formation
Genus

! Species

! Location

! Stratigraphic position

! Abundance

!Material

! Notes

!Images

Acipenser

|A. cf. albertensis

|

|Maastrichtian

|

|

|A sturgeon.

|frameless

Anomoeodus

|A. phaseolus

|

|Maastrichtian, potentially Danian

|

|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.

|File:Anomoeodus subclavatus.jpg

Atractosteus

|A. sp.

|

|Maastrichtian & Danian

|

|11 teeth

|A gar. First record of gars from eastern North America during the Paleocene.

|frameless

cf. Bananogmius

|cf. B. sp.

|

|Maastrichtian

|

|

|A plethodid tselfatiiform.

|frameless

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.

|

rowspan="2" |Enchodus

|E. ferox

|

| rowspan="2" |Maastrichtian

|

|

| rowspan="2" |An enchodontid aulopiform. The E. gladiolus remains are the first record of the species in eastern North America.

| rowspan="2" |frameless

E. gladiolus

|

|

|8 teeth

Iridopristis

|I. parrisi

|Sewell, New Jersey

|Danian

|

|3 partial articulated specimens, including a near-complete skull.

|A stem-lineage member of Holocentridae. The earliest known definitive holocentrid. Type locality for genus and species.

|

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.

|

Phyllodus

|P. paulkatoi

|

| Maastrichtian

|

|1 tooth plate

|A phyllodontid elopomorph. First known occurrence in eastern North America.

|

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.

|frameless

=Reptiles=

== Birds ==

A number of fossil birds are known from the greensands of the formation. The Hornerstown serves as the type locality for all these genera and species:

class="wikitable" align="center" width="100%"
colspan="7" align="center" |Birds of the Hornerstown Formation
Genus

! Species

! Location

! Stratigraphic position

! Abundance

! Notes

Anatalavis

|

A. rex

|

| rowspan="8" |?earliest Paleocene{{cite journal |last1=Olson |first1=S. |year=1994 |title=A giant Presbyornis (Aves: Anseriformes) and other birds from the Paleocene Aquia Formation of Maryland and Virginia |journal=Proceedings of the Biological Society of Washington |volume=107 |pages=429–435 |hdl=10088/6493}}{{Cite journal |last1=Brocklehurst |first1=Neil |last2=Upchurch |first2=Paul |last3=Mannion |first3=Philip D. |last4=O'Connor |first4=Jingmai |date=2012-06-25 |title=The Completeness of the Fossil Record of Mesozoic Birds: Implications for Early Avian Evolution |journal=PLOS ONE |language=en |volume=7 |issue=6 |pages=e39056 |doi=10.1371/journal.pone.0039056 |doi-access=free |issn=1932-6203 |pmc=3382576 |pmid=22761723|bibcode=2012PLoSO...739056B }}

|

|A waterfowl potentially related to the magpie-goose."3.22 New Jersey, United States; 7. Hornerstown Formation," in Weishampel, et al. (2004). Page 586.

Graculavus

|

G. velox

|

|

|A potential wader.

Laornis

|

L. edwardsianus

|

|

|A laornithid wading bird.

Novacaesareala

|N. hungerfordi

|

|

|A potential tropicbird.

rowspan="2" |

Palaeotringa

|

P. littoralis

|

|

| rowspan="2" |A potential wader.

P. vagans

|

|

Telmatornis

|

T. priscus

|

|

|A potential wader.

Tytthostonyx

|

T. glauconiticus

|

|

|A potential seabird.

== Non-avian dinosaurs ==

class="wikitable" align="center" width="100%"
colspan="7" align="center" |Dinosaurs of the Hornerstown Formation
Genus

! Species

! Location

! Stratigraphic position

! Abundance

! Notes

Hadrosauridae indet.

|

|

|Maastrichtian

|

|A hadrosaurid ornithischian.

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.{{cite journal |last1=Olsson |first1=R.K. |year=1960 |title=Foraminifera of latest Cretaceous and earliest Tertiary age in the New Jersey coastal plain |journal=Journal of Paleontology |volume=34 |pages=1–58}}

== Crocodylomorphs ==

class="wikitable" align="center" width="100%"
colspan="9" align="center" |Crocodylomorphs of the Hornerstown Formation
Genus

! Species

! Location

! Stratigraphic position

! Abundance

!Material

! Notes

!Images

Borealosuchus

|B. threeensis

|

|Maastrichtian

|

|Lower jaw, postcranial remains

|A eusuchian. Type locality of species.{{Cite journal |last1=Brochu |first1=Christopher A. |last2=Parris |first2=David C. |last3=Grandstaff |first3=Barbara Smith |last4=Denton |first4=Robert K. |last5=Gallagher |first5=William B. |date=2012 |title=A new species of Borealosuchus (Crocodyliformes, Eusuchia) from the Late Cretaceous–early Paleogene of New Jersey |url=http://www.tandfonline.com/doi/abs/10.1080/02724634.2012.633585 |journal=Journal of Vertebrate Paleontology |language=en |volume=32 |issue=1 |pages=105–116 |doi=10.1080/02724634.2012.633585 |bibcode=2012JVPal..32..105B |issn=0272-4634|url-access=subscription }}

|frameless

rowspan="2" |

Bottosaurus

|

B. harlani

|

|Maastrichtian & Danian

|

| rowspan="2" |Remains including lower jaw of a juvenile individualCossette, 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.

| rowspan="2" |An early caiman.

| rowspan="2" |

B. tuberculatus

|

|Maastrichtian

|

Hyposaurus

|H. rogersii

|

|Maastrichtian & Danian

|

|

|A dyrosaurid.{{Cite journal |last=Morgan |first=Donald J |date=December 2018 |title=PRESENCE OF A DYROSAURID NEOSUCHIAN IN THE SEVERN/BRIGHTSEAT FORMATION OF MARYLAND |url=https://www.researchgate.net/publication/331315226 |journal=The Journal of the Delaware Valley Paleontological Society |volume=X |pages=91 to 104}}

|

cf. Procaimanoidea

|P. sp.

|

|Maastrichtian

|

|

|A caiman.

|File:NMNH-USNM15996 1.jpg

Thoracosaurus

|T. neocesariensis

|

|Maastrichtian & Danian

|

|

|A gavialoid.

|frameless

== Plesiosaurs ==

class="wikitable" align="center" width="100%"
colspan="9" align="center" |Plesiosaurs of the Hornerstown Formation
Genus

! Species

! Location

! Stratigraphic position

! Abundance

!Material

! Notes

!Images

"Plesiosaurus"

|"P." brevifemur

|

|Maastrichtian

|

|

|An indeterminate plesiosaur known from a well-documented specimen, now lost.{{Cite web |title=PBDB Collection |url=https://paleobiodb.org/classic/basicCollectionSearch?collection_no=167780 |access-date=2024-11-12 |website=paleobiodb.org}}{{Cite journal |last=Parris |first=David C. |date=1974 |title=Additional Records of Plesiosaurs from the Cretaceous of New Jersey |url=https://www.jstor.org/stable/1303102 |journal=Journal of Paleontology |volume=48 |issue=1 |pages=32–35 |jstor=1303102 |issn=0022-3360}}

|

== Turtles ==

class="wikitable" align="center" width="100%"
colspan="8" align="center" |Testudines of the Hornerstown Formation
Genus

! Species

! Location

! Stratigraphic position

! Abundance

! Notes

!Images

rowspan="3" |Adocus

|A. agilis

|

| rowspan="3" |Maastrichtian

|

| rowspan="3" |An adocid.

| rowspan="3" |frameless

A. beatus

|

|

A. syntheticus

|

|

Agomphus

|A. pectoralis

|

|Maastrichtian

|

|A kinosternoid related to Dermatemys.{{Cite web |title=PBDB Taxon |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=37653 |access-date=2024-11-11 |website=paleobiodb.org}}

|File:Agomphus.jpg

Bothremys

|B. sp.

|

|Maastrichtian

|

|A bothremydid side-necked turtle.

|

Euclastes

|E. wielandi

|

|Maastrichtian & Danian

|

|A sea turtle.

|File:Euclastes sp.jpg

Lytoloma

|L. jeanesii

|

|Maastrichtian

|

|A sea turtle.

|

Osteopygis

|O. emarginatus

|

|Maastrichtian

|

|A macrobaenid.

|

Peritresius

|P. ornatus

|

|Maastrichtian

|

|A sea turtle.

|

rowspan="2" |Taphrosphys

|T. sulcatus

|

| rowspan="2" |Maastrichtian

|

| rowspan="2" |A bothremydid side-necked turtle.

|

T. strenuus

|

|

|

== Mosasaurs ==

class="wikitable" align="center" width="100%"
colspan="9" align="center" |Mosasaurs of the Hornerstown Formation
Genus

! Species

! Location

! Stratigraphic position

! Abundance

!Material

! Notes

!Images

Halisaurus

|H. platyspondylus

|

|Maastrichtian

|

|

|A halisaurine. Type locality of the genus and species.

|frameless

Mosasaurus

|M. hoffmanni (=Nectoportheus validus)

|

| Maastrichtian

|

|Pterygoid, teeth, vertebrae

|A mosasaurine. This formation contains some of the last known remains, comprising individuals killed during the mass mortality event that formed the MFL. A very large specimen is known.

|frameless

Plioplatecarpus

|P. sp.

|

|Maastrichtian

|

|

|A plioplatecarpine.

|frameless

See also

{{Portal|Earth sciences|Paleontology|Dinosaurs}}

References

{{Reflist}}

= Bibliography =

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

Category:Danian Stage

Category:Maastrichtian Stage of North America

Category:Paleocene Series of North America

Category:Cretaceous geology of New Jersey

Category:Paleogene geology of New Jersey

Category:Cretaceous–Paleogene boundary

Category:Shallow marine deposits

Category:Marl formations