Yes, Horsehead Philodendron is toxic to dogs!
Dogs accidentally consuming the Horsehead Philodendron plants can show the following clinical symptoms: Vomiting, Prolonged Depression, Incoordination, Hypersalivaton, Sleepiness Or Excitation, Dilated Pupils, Low Body Temperature, Low Blood Pressure, Coma, Seizure And Death (In Rare Cases).
Horsehead Philodendron consumption is also toxic to Cats.
Toxic Principles Of Horsehead Philodendron: Insoluble calcium oxalates.
More Info About The Horsehead Philodendron Plant
Scientific Name: Philodendron bipennifolium
Family: Araceae.
Also known as: Fiddle-Leaf, Cordatum, Heartleaf Philodendron, Panda Plant, Split Leaf Philodendron, Fruit Salad Plant, Red Emerald, Red Princess, Saddle Leaf.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.