Please Help Identify This Dense Heavy Object I Found On The Shore In Venice After A Storm.

[matty34]

I found this fossil or bone I think on the beach in Venice Florida after a storm. It is black in color but you can see white on the inside where it has chipped off. It is veeeery heavy for its size. I have found countless sharks teeth on this beach but never something like this. It's been driving me crazy for years. It appears to have an inner core and An outer core.

More information for you guys to chew on. If you zoom in on the last picture you can see the white bone material I was talking about. Also there is a square nodule on the top of the bone that you can see in picture one. So that being said, it looks like it has three layers to it. An outer core, middle and inner core. I don't know. It's weird.

If you look closely the surface is slick yet porous textured. It does fracture off concoidally like flint or glass would. But that really does not explain the shape. It is obviously not a natural rock formation. It is perfectly arched. Almost like a cross section of a hollow bone of some sort. Or it was something organic that grew around something round. The only two things I can think of that have this shape are bone and maybe a tree or branch. I have seen petrified wood before and this does not have those characteristics though. ( wood grain and such ). This led me to the conclusion that it was mammal or reptile in nature. What do you think?

[mikeymig]

Partial ivory tusk.

mikey

[tmaier]

Ivory normally shows a wood-like grain along a fracture line

and a curious cross hatch pattern at a break

[Auspex]

Schreger lines are a defining characteristic: LINK

[tmaier]

Oh... I've been calling them Maier Hatches.

[Boesse]

It's possible that this could be a small proboscidean tusk, or a walrus tusk. Because it's missing the middle of the tusk, it's not possible to tell whether or not it had a core of globular dentine (a structure unique to walruses of the tribe Odobenini consisting of little spherules of dentine). If the latter, it is more likely to represent Pleistocene Odobenus rosmarus rather than Pliocene Ontocetus/Alachtherium, owing to to the straightness of the tusk fragment (Ontocetus/Alachtherium tusks are more curved and the curvature is evident even in fragmentary specimens like this).

[jpevahouse]

Nice find, definitely a well worn piece of elephant tusk. Elephant tusks, like trees, grow a ring each year. The rings tend to separate with age on fossil tusks. The pattern of the surface of the rings is very distinct. I have a couple of fossil walrus tusk sections found off shore NJ. They are quiet different from elephant tusk. I don't remember seeing walrus fossils from the coast of Florida. They usually lived in colder climate farther north during the ice age, north of the Carolinas.

Edited September 16, 2014 by jpevahouse

[jpevahouse]

Ivory normally shows a wood-like grain along a fracture line

TUSK3.JPG

and a curious cross hatch pattern at a break

TUSK2.JPG

I think the cross hatching pattern distinquishes between mammoth and mastodon?

Edited September 16, 2014 by jpevahouse

[tmaier]

I thought it applied to all elephantine ivory.

[Auspex]

The intersecting angle of the lines can differentiate between Mastodon and Mammoth.

I also wondered about Walrus, as the core is missing. I agree that it is a possibility.

[siteseer]

Walrus fossils have been found in Florida including Venice and the phosphate mines (Pliocene, Whiddon Creek Fauna). One of the Tampa Bay Fossil Club members found a piece of walrus tusk in one of the shell pits too. I think it was at APAC - Calousahatchee Formation.

Nice find, definitely a well worn piece of elephant tusk. Elephant tusks, like trees, grow a ring each year. The rings tend to separate with age on fossil tusks. The pattern of the surface of the rings is very distinct. I have a couple of fossil walrus tusk sections found off shore NJ. They are quiet different from elephant tusk. I don't remember seeing walrus fossils from the coast of Florida. They usually lived in colder climate farther north during the ice age, north of the Carolinas.

[Harry Pristis]

I didn't think that walrus ivory has Schreger lines. Does it, Bobby?

[matty34]

Wow!!!!! You guys are awesome. Obviously, since I know nothing about this type of stuff I'll let you duke it out and I'll stand by and read. . It's really cool that I could be holding something that old. I am going to look up some of the scientific names you mentioned with pictures now. Very exciting stuff. I can't thank you enough. Now I've got the bug. Lol.

[matty34]

I also guess we are all in agreement that it is petrified ivory?

[matty34]

Another photo of the item in question showing scheger lines?

Edited September 17, 2014 by matty34

[matty34]

...and one more

[tmaier]

Notice that your ivory also has very neatly drilled holes in it. Those are caused by the action of boring clams.

[Boesse]

Hey all,

One thing I didn't look at long enough at first was how small (i.e. small a proportion of the cross-section) this tusk fragment was: it's something like 1/3 of the circumference of the tusk, which would make this thing about 5" across in maximum diameter (or even slightly larger?). Anyway... that's really pushing it for a walrus tusk (I've seen some approach or slightly exceed 4"). So, proboscidean seems more likely.

I don't know if walrus tusks have hunter-schreger bands - a quick glance through Ray (1975) showed some cross-sections of Odobenus tusks and no obvious bands were visible - so, that is likely a good feature for east coasters to use for identifying fragmentary tusks in the walrus-proboscidean overlap size range (big walrus/little elephant). Of course, globular dentine is even better.

Otherwise - fossils of Ontocetus / Alachtherium have been found as far south as Florida (a complete list of specimens are given in Kohno and Ray (2008) in the Lee Creek IV volume). As far as I know, the southernmost record of Odobenus in the Atlantic Coastal Plaine is Edisto Island, Georgia. Floridan specimens remain a possibility, but as far as I know the youngest (and only) walruses in Floridan latitudes were there in the Pliocene ( Ontocetus /Alachtherium is strictly Pliocene while Odobenus is strictly Pleistocene in the North Atlantic - although the two co-occur in the Pliocene of Japan).

[tmaier]

I'll let you duke it out and I'll stand by and read. .

Yeah, that's what I'm doing right now, I've already given out all the info I know in this area. These threads often swing back and forth for a while, and then stabilize out to the best answers after a few days. It's like sausage being made...

[matty34]

Thanks for the extra info on the clams. I have always wondered about that.

Edited September 17, 2014 by matty34

[matty34]

Yeah, that's what I'm doing right now, I've already given out all the info I know in this area. These threads often swing back and forth for a while, and then stabilize out to the best answers after a few days. It's like sausage being made...

You guys are like scientific prize fighters trading academic punches back and forth. This forum is way more informative than I expected.

[tmaier]

No, you have the wrong idea about this. Ive been involved in research since I was a teenager, and when people are doing this they are not fighting, as long as they are doing it right. A team activity like this is more the equivalent of trying to drag logs out of the woods, each person is tugging on the load to bring it closer to the road.

sometimes you never reach the raod, and you get stuck deep in the woods...

people here are playing, not fighting.

[matty34]

No, you have the wrong idea about this. Ive been involved in research since I was a teenager, and when people are doing this they are not fighting, as long as they are doing it right. A team activity like this is more the equivalent of trying to drag logs out of the woods, each person is tugging on the load to bring it closer to the road.

sometimes you never reach the raod, and you get stuck deep in the woods...

people here are playing, not fighting.

I meant no offense. Just in awe of the thoroughness here. Wrong choice of words.

[Harry Pristis]

Hey all,

One thing I didn't look at long enough at first was how small (i.e. small a proportion of the cross-section) this tusk fragment was: it's something like 1/3 of the circumference of the tusk, which would make this thing about 5" across in maximum diameter (or even slightly larger?). Anyway... that's really pushing it for a walrus tusk (I've seen some approach or slightly exceed 4"). So, proboscidean seems more likely.

I don't know if walrus tusks have hunter-schreger bands - a quick glance through Ray (1975) showed some cross-sections of Odobenus tusks and no obvious bands were visible - so, that is likely a good feature for east coasters to use for identifying fragmentary tusks in the walrus-proboscidean overlap size range (big walrus/little elephant). Of course, globular dentine is even better.

Otherwise - fossils of Ontocetus / Alachtherium have been found as far south as Florida (a complete list of specimens are given in Kohno and Ray (2008) in the Lee Creek IV volume). As far as I know, the southernmost record of Odobenus in the Atlantic Coastal Plaine is Edisto Island, Georgia. Floridan specimens remain a possibility, but as far as I know the youngest (and only) walruses in Floridan latitudes were there in the Pliocene ( Ontocetus /Alachtherium is strictly Pliocene while Odobenus is strictly Pleistocene in the North Atlantic - although the two co-occur in the Pliocene of Japan).

Hulbert (2001) lists two odobenins from Florida, Trichechodon huxleyi, probably Early Pliocene, and an undescribed species from the Early Pleistocene. Maybe this later walrus has now been described. Walrus are rare fossils in Florida.

[Boesse]

Hey Harry,

Thanks for that - I always forget about Hulbert. Kohno and Ray (2008) referred all Pliocene walrus material from the North Atlantic - including everything from the Pliocene of Florida - to Ontocetus emmonsi. "Trichecodon" huxleyi is sort of a garbage can taxon which was synonymized with Odobenus rosmarus by Demere (1994) - the name was originally meant to apply to Odobenus-like tusks with thin cementum, but often uncritically applied including to transversely narrow, longitudinally grooved and highly curved tusks of Ontocetus emmonsi. Ontocetus emmonsi was originally named on a tusk fragment thought to be a sperm whale and then thought to be a sirenian; Kohno and Ray (2008) synonymized Prorosmarus alleni, Alachtherium cretsii, Alachtherium antverpiensis (synyonymized with A. cretsii by Demere), and Alactherium africanus (walrus from Morocco, of all places!). All of these have a similar mandible and identical tusk morphology, although some other odobenid specialists prefer the name Alachtherium cretsii as the holotype specimen is more diagnostic. Demere (1994) and Kohno and Ray (2008) considered all North Atlantic Pleistocene specimens to probably represent Odobenus rather than Ontocetus.

So, unless that early Pleistocene specimen was referred to Ontocetus (i.e. in the offhand chance that the age determination has been refined to Pliocene in the last decade or so), it would most likely represent Odobenus rosmarus.

I hope the above discussion helps sort out some of the recent clarifications in Atlantic walrus taxonomy. Bobby